PIONEER HIGH INCOME FUND, INC.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM

N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number

811-21043

Pioneer High Income Fund, Inc.

(Exact name of registrant as specified in charter)

60 State Street, Boston, MA 02109

(Address of principal executive offices) (ZIP code)

Christopher J. Kelley, Amundi Asset Management, Inc.,

60 State Street, Boston, MA 02109

(Name and address of agent for service)

Registrant’s telephone number, including area code: (617)

742-7825

Date of fiscal year end: March 31, 2025

Date of reporting period: April 1, 2024 through September 30, 2024

Form

N-CSR

is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule

30e-1

under the Investment Company Act of 1940 (17 CFR

270.30e-1). The

Commission may use the information provided on Form

N-CSR

in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form

N-CSR,

and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form

N-CSR

unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. ss. 3507.

ITEM 1. REPORT TO STOCKHOLDERS.

Pioneer High Income Fund, Inc.

Semiannual Report | September 30, 2024

Ticker Symbol: PHT

visit us: www.amundi.com/us

Table of Contents

Portfolio Management Discussion	2
Portfolio Summary	9
Prices and Distributions	10
Performance Update	11
Schedule of Investments	12
Financial Statements	37
Notes to Financial Statements	43
Additional Information (unaudited)	65
Approval of Renewal of Investment Management Agreement	68
Directors, Officers and Service Providers	73

Pioneer High Income Fund, Inc. |

Semiannual Report

9/30/24

Q	How did the Fund perform during the six-month period ended September 30, 2024?
A	Pioneer High Income Fund, Inc. returned 7.97% at net asset value (NAV) and 9.02% at market price during the six-month period ended September 30, 2024. During the same six-month period, the Fund’s benchmark, the ICE Bank of America US High Yield Index (the ICE BofA Index), returned 5.66% at NAV. The ICE BofA Index is an unmanaged measure of the performance of high-yield securities. Unlike the Fund, the ICE BofA Index does not use leverage. While the use of leverage increases investment opportunity, it also increases investment risk.
	During the same six-month period, the average return at NAV of the 39 closed end funds in Morningstar’s High Yield Bond Closed End Funds category (which may or may not be leveraged) was 7.66%, while the same closed end fund Morningstar category’s average return at market price was 9.07%. The shares of the Fund were selling at a 5.33% discount to NAV on September 30, 2024. Comparatively, the Fund’s shares were selling at a discount to NAV of 6.24% on March 31, 2024. On September 30, 2024, the standardized 30-day SEC yield of the Fund’s shares was 7.32%*.
Q	Which of the Fund’s investment strategies contributed positively to the Fund’s benchmark-relative performance during the six-month period ended September 30, 2024?
A	The Fund carries leveraged exposure to the high yield corporate bond market, which proved additive to benchmark-relative

	returns during the six-month period, driven by the market’s positive performance during the period. With respect to ratings categories, the Fund’s tilt toward lower quality issues within the high yield corporate bond market benefited benchmark-relative results during the six-month period, as non-rated issues outperformed the higher-rated “BB” issues in which the Fund was underweight. In sector terms, the Fund’s underweight allocations to the retail, capital goods and automotive sectors, as well as an overweight to the insurance sector, contributed positively to the Fund’s benchmark-relative returns during the six-month period. Finally, the Fund’s benchmark-relative returns benefited from out-of-benchmark allocations to insurance-linked securities, as returns experienced by the Fund’s holdings within the category exceeded those of the broader high yield corporate bond market during the six-month period.
	Top performing individual securities included TMS International, which provides industrial steel mill services, and Trinity Industrial, within the machinery subsector, as both had strong earnings reported during the period.
Q	Which investment strategies detracted from the Fund’s benchmark-relative performance results during the six-month period ended September 30, 2024?
A	The main factor that held back the performance of the Fund was that the duration of the Fund ’ s portfolio was shorter than that of the benchmark. As US Treasury yields and spreads fell, this held back the performance of the Fund. The Fund typically maintains a shorter duration relative to the benchmark in an effort to reduce volatility in the Fund ’ s portfolio, as the leverage that the Fund employs increases the volatility of the Fund ’ s portfolio.
	Overweight exposure to the energy sector, and underweight exposure to the telecommunications and media sectors, were the largest detractors from benchmark-relative performance during the six-month period. The individual securities that detracted most from the benchmark-relative performance during the period were within the consumer goods, healthcare and basic industry sectors.
	A top detractor from the Fund’s performance on an individual security basis was Spectrum Brands, which is categorized as

	personal & household products subsector within the consumer goods sector. It was anticipated that the company would utilize cash proceeds to buy back existing debt, but this did not materialize.
Q	Did the Fund’s distributions** to stockholders change during the six-month period ended September 30, 2024?
A	The Fund’s monthly distribution rate remained at $0.0550 per share over the course of the six-month period.
Q	How did the level of leverage in the Fund change during the six-month period ended September 30, 2024?
A	The Fund employs leverage through a credit agreement. As of September 30, 2024, 30.4% of the Fund’s total managed assets were financed by leverage, or borrowed funds, compared with 31.2% of the Fund’s total managed assets financed by leverage at the start of the six-month period on April 1, 2024. The change in the percentage of the Fund’s total managed assets financed by leverage during the six-month period was the result of an increase in the value of the Fund’s total managed assets relative to the absolute amount of funds borrowed. The interest rate on the Fund’s leverage decreased by 1 basis points from March 31, 2024 to September 30, 2024.
Q	Did the Fund have any exposure to derivatives during the six- month period ended September 30, 2024?
A	Yes, we invested the Fund’s portfolio in forward foreign currency exchange contracts (currency forwards) and other currency related derivatives during the period, which had a positive effect on benchmark-relative performance. These investments were made to hedge positions bought in non-dollar securities. In addition, the Fund’s small position in credit default swaps contributed modestly to relative returns.
Q	What is your investment outlook, and how is the Fund positioned heading into the second half of its fiscal year?
A	The US economy has experienced stronger growth than anticipated this year, but is gradually decelerating. The once-

	We do not believe that the high yield market will perform as poorly as it has historically performed in a recession. Credit quality is currently higher than it has been historically, featuring more BB-rated (higher quality) credits and a reduced number of CCC-rated (lower quality) credits. Secondly, issuance has been focused on refinancing debt, rather than adding debt for acquisitions or other purposes.
	The very tight levels of spreads is a concern. Yields remain attractive, but spreads are in the tightest decile historically. They are pricing in defaults falling back to non-recessionary levels (2-3%) versus the average levels we are currently experiencing. We do not expect a significant decrease in the number of defaults until profits recover across the economy. We have sought to reduce risk in the Fund’s portfolio relative to recent periods, and sought to maintain a high level of yield. This will allow us to add risk to the Fund’s portfolio if the market sells off to levels that price in some margin of error.
	The main focus of the Fund continues to be income and the higher level of interest rates has helped. Our cost of leverage has declined slightly as the Fed has begun the process of easing. This should allow some flexibility, although it might be accompanied by a more difficult environment for high yield bonds. While the market has been “risk on” in the last year, we believe security selection will be more important going forward, and we’ve seen distressed securities struggle lately. Our team of analysts will focus on identifying mispriced securities to help the Fund perform.

(As a percentage of total investments)*
1.	Hercules LLC, 6.50%, 6/30/29	1.22%
2.	Prime Security Services Borrower LLC/Prime Finance, Inc., 6.25%, 1/15/28 (144A)	1.19
3.	Hanover Insurance Group, Inc., 7.625%, 10/15/25	1.11
4.	Liberty Mutual Group, Inc., 10.75% (3 Month Term SOFR + 738 bps), 6/15/58 (144A)	1.06
5.	Kennedy-Wilson, Inc., 5.00%, 3/1/31	1.03
6.	McGraw-Hill Education, Inc., 8.00%, 8/1/29 (144A)	1.01
7.	Limak Cimento Sanayi ve Ticaret AS, 9.75%, 7/25/29 (144A)	1.00
8.	Provident Funding Associates LP/PFG Finance Corp., 6.375%, 6/15/25 (144A)	0.98
9.	Prime Healthcare Services, Inc., 9.375%, 9/1/29 (144A)	0.94
10.	Grupo Aeromexico SAB de CV, 8.50%, 3/17/27 (144A)	0.94

	9/30/24	3/31/24
Market Value	$ 8.00	$ 7.66
Discount	(5.33)%	(6.24)%

	Net Investment Income	Short-Term Capital Gains	Long-Term Capital Gains
4/1/24 – 9/30/24	$0.3300	$—	$—

Average Annual Total Return (As of September 30, 2024)
Period	Net Asset Value (NAV)	Market Price	ICE BofA U.S. High Yield Index
10 Years	5.11%	2.12%	4.95%
5 Years	6.36	6.90	4.55
1 Year	20.62	30.20	15.66

Principal Amount USD ($)		Value
	UNAFFILIATED ISSUERS — 142.8%^
	Senior Secured Floating Rate Loan Interests — 2.0% of Net Assets*(a)
	Auto Parts & Equipment — 0.5%
1,375,628	First Brands Group LLC, First Lien 2021 Term Loan, 10.514% (Term SOFR + 500 bps), 3/30/27	$ 1,364,117
	Total Auto Parts & Equipment	$ 1,364,117


	Casino Hotels — 0.6%
1,492,268	Century Casinos, Inc., Term B Facility Loan, 11.301% (Term SOFR + 600 bps), 4/2/29	$ 1,428,847
	Total Casino Hotels	$ 1,428,847


	Computer Services — 0.1%
380,000(b)	Amazon Holdco, Inc., Seven-Year Term Loan, 7/30/31	$ 379,287
	Total Computer Services	$ 379,287


	Cruise Lines — 0.3%
840,000	LC Ahab US Bidco LLC, Initial Term Loan, 8.345% (Term SOFR + 350 bps), 5/1/31	$ 844,725
	Total Cruise Lines	$ 844,725


	Electric-Generation — 0.3%
675,000(b)	Alpha Generation LLC, Term Loan B, 9/19/31	$ 675,844
	Total Electric-Generation	$ 675,844


	Medical-Drugs — 0.2%
390,000	Endo Finance Holdings, Inc., Initial Term Loan, 9.783% (Term SOFR + 450 bps), 4/23/31	$ 390,122
	Total Medical-Drugs	$ 390,122


	Total Senior Secured Floating Rate Loan Interests (Cost $5,078,633)	$ 5,082,942

Shares
	Common Stocks — 0.5% of Net Assets
	Chemicals — 0.0% †
22	LyondellBasell Industries NV, Class A	$ 2,110
	Total Chemicals	$ 2,110

Shares		Value
	Communications Equipment — 0.0% †
2,630 +	Digicel International Finance Ltd.	$ 6,575
	Total Communications Equipment	$ 6,575


	Diversified Telecommunication Services — 0.0% †
251,944 +	Atento S.A.	$ 7
	Total Diversified Telecommunication Services	$ 7


	Oil, Gas & Consumable Fuels — 0.0% †
21(c)	Amplify Energy Corp.	$ 137
8,027	Petroquest Energy, Inc.	1,405
	Total Oil, Gas & Consumable Fuels	$ 1,542


	Passenger Airlines — 0.5%
57,203	Grupo Aeromexico SAB de CV	$ 1,283,122
	Total Passenger Airlines	$ 1,283,122


	Pharmaceuticals — 0.0% †
2,975(c)	Endo, Inc.	$ 75,804
	Total Pharmaceuticals	$ 75,804


	Total Common Stocks (Cost $1,479,274)	$ 1,369,160

Principal Amount USD ($)
	Asset Backed Securities — 0.6% of Net Assets
1,443,149	Santander Bank Auto Credit-Linked Notes, Series 2023-B, Class F, 12.24%, 12/15/33 (144A)	$ 1,494,135
	Total Asset Backed Securities (Cost $1,443,149)	$ 1,494,135


	Collateralized Mortgage Obligations—2.3% of Net Assets
710,000(a)	Connecticut Avenue Securities Trust, Series 2021-R01, Class 1B2, 11.28% (SOFR30A + 600 bps), 10/25/41 (144A)	$ 747,491
430,000(a)	Federal Home Loan Mortgage Corp. STACR REMIC Trust, Series 2021-DNA7, Class B2, 13.08% (SOFR30A + 780 bps), 11/25/41 (144A)	465,883
450,000(a)	Federal Home Loan Mortgage Corp. STACR REMIC Trust, Series 2021-HQA3, Class B2, 11.53% (SOFR30A + 625 bps), 9/25/41 (144A)	471,266

Principal Amount USD ($)		Value
	Collateralized Mortgage Obligations— (continued)
610,000(a)	Federal Home Loan Mortgage Corp. STACR REMIC Trust, Series 2022-DNA2, Class B2, 13.78% (SOFR30A + 850 bps), 2/25/42 (144A)	$ 670,998
1,370,000(a)	Federal Home Loan Mortgage Corp. STACR Trust, Series 2019-DNA3, Class B2, 13.545% (SOFR30A + 826 bps), 7/25/49 (144A)	1,568,650
120,000(a)	Federal National Mortgage Association Connecticut Avenue Securities, Series 2021-R02, Class 2B2, 11.48% (SOFR30A + 620 bps), 11/25/41 (144A)	126,191
1,350,000(a)	STACR Trust, Series 2018-HRP2, Class B2, 15.895% (SOFR30A + 1,061 bps), 2/25/47 (144A)	1,638,625
	Total Collateralized Mortgage Obligations (Cost $5,231,268)	$ 5,689,104


	Commercial Mortgage-Backed Securities—2.5% of Net Assets
1,415,000(a)	Capital Funding Mortgage Trust, Series 2021-19, Class B, 20.41% (1 Month Term SOFR + 1,521 bps), 10/27/24 (144A)	$ 1,406,411
890,204(d)	FREMF Mortgage Trust, Series 2019-KJ24, Class B, 7.60%, 10/25/27 (144A)	837,941
1,499,131(a)	FREMF Mortgage Trust, Series 2019-KS12, Class C, 12.361% (SOFR30A + 701 bps), 8/25/29	1,438,456
222,712(a)	FREMF Mortgage Trust, Series 2020-KF74, Class C, 11.711% (SOFR30A + 636 bps), 1/25/27 (144A)	205,284
317,897(a)	FREMF Mortgage Trust, Series 2020-KF83, Class C, 14.461% (SOFR30A + 911 bps), 7/25/30 (144A)	300,442
2,500,000	Wells Fargo Commercial Mortgage Trust, Series 2015-C28, Class E, 3.00%, 5/15/48 (144A)	1,970,550
	Total Commercial Mortgage-Backed Securities (Cost $6,329,737)	$ 6,159,084

Principal Amount USD ($)		Value
	Convertible Corporate Bonds — 2.7% of Net Assets
	Banks — 0.0% †
IDR 1,422,679,000	PT Bakrie & Brothers Tbk, 12/31/24	$ 7,142
	Total Banks	$ 7,142


	Chemicals — 1.7%
4,000,000(e)	Hercules LLC, 6.50%, 6/30/29	$ 4,248,381
	Total Chemicals	$ 4,248,381


	Commercial Services — 0.5%
1,130,000	Global Payments, Inc., 1.50%, 3/1/31 (144A)	$ 1,079,150
	Total Commercial Services	$ 1,079,150


	Entertainment — 0.5%
1,455,000(f)	DraftKings Holdings, Inc., 3/15/28	$ 1,259,302
	Total Entertainment	$ 1,259,302


	Total Convertible Corporate Bonds (Cost $5,634,248)	$ 6,593,975


	Corporate Bonds — 123.3% of Net Assets
	Advertising — 3.3%
2,090,000	Clear Channel Outdoor Holdings, Inc., 7.50%, 6/1/29 (144A)	$ 1,800,030
1,470,000	Neptune Bidco US, Inc., 9.29%, 4/15/29 (144A)	1,439,938
2,010,000	Stagwell Global LLC, 5.625%, 8/15/29 (144A)	1,943,305
3,000,000	Summer BC Bidco B LLC, 5.50%, 10/31/26 (144A)	2,964,214
	Total Advertising	$ 8,147,487


	Aerospace & Defense — 1.5%
2,150,000	Bombardier, Inc., 6.00%, 2/15/28 (144A)	$ 2,164,214
246,000	Bombardier, Inc., 7.125%, 6/15/26 (144A)	249,774
740,000	Spirit AeroSystems, Inc., 9.375%, 11/30/29 (144A)	802,790
592,000	Triumph Group, Inc., 9.00%, 3/15/28 (144A)	619,715
	Total Aerospace & Defense	$ 3,836,493

Principal Amount USD ($)		Value
	Airlines — (continued)
3,001,186(a)	Gol Finance S.A., 15.344% (1 Month Term SOFR + 1,050 bps), 1/29/25 (144A)	$ 3,181,257
3,255,000	Grupo Aeromexico SAB de CV, 8.50%, 3/17/27 (144A)	3,289,220
330,000	Latam Airlines Group S.A., 13.375%, 10/15/29 (144A)	383,913
759,000	Mileage Plus Holdings LLC/Mileage Plus Intellectual Property Assets, Ltd., 6.50%, 6/20/27 (144A)	768,437
EUR 1,600,000	Transportes Aereos Portugueses S.A., 5.625%, 12/2/24 (144A)	1,779,259
	Total Airlines	$ 11,837,720


	Auto Manufacturers — 0.4%
1,035,000	JB Poindexter & Co., Inc., 8.75%, 12/15/31 (144A)	$ 1,094,268
	Total Auto Manufacturers	$ 1,094,268


	Auto Parts & Equipment — 0.6%
1,285,000	Adient Global Holdings, Ltd., 8.25%, 4/15/31 (144A)	$ 1,363,385
	Total Auto Parts & Equipment	$ 1,363,385


	Banks — 3.7%
600,000(d)(h)	Bank of America Corp., 6.50% (3 Month Term SOFR + 444 bps)	$ 599,858
EUR 2,400,000 (d)(h)	CaixaBank S.A., 3.625% (5 Year EUR Swap + 386 bps)	2,377,515
1,175,000	Freedom Mortgage Corp., 12.25%, 10/1/30 (144A)	1,315,947
675,000(d)(h)	Intesa Sanpaolo S.p.A., 7.70% (5 Year USD Swap Rate + 546 bps) (144A)	674,177
1,975,000	KeyBank N.A., 4.90%, 8/8/32	1,922,533
410,000(d)	Toronto-Dominion Bank, 7.25% (5 Year CMT Index + 298 bps), 7/31/84	427,159
1,240,000(d)	Toronto-Dominion Bank, 8.125% (5 Year CMT Index + 408 bps), 10/31/82	1,330,287
545,000(d)(h)	UBS Group AG, 9.25% (5 Year CMT Index + 476 bps) (144A)	642,737
	Total Banks	$ 9,290,213

Principal Amount USD ($)		Value
	Biotechnology — 0.3%
EUR 745,000	Cidron Aida Finco S.a.r.l., 5.00%, 4/1/28 (144A)	$ 805,537
	Total Biotechnology	$ 805,537


	Building Materials — 3.5%
1,991,000	AmeriTex HoldCo Intermediate LLC, 10.25%, 10/15/28 (144A)	$ 2,082,751
2,211,000	Cornerstone Building Brands, Inc., 6.125%, 1/15/29 (144A)	1,956,408
1,140,000	Knife River Corp., 7.75%, 5/1/31 (144A)	1,212,076
3,550,000	Limak Cimento Sanayi ve Ticaret AS, 9.75%, 7/25/29 (144A)	3,477,765
	Total Building Materials	$ 8,729,000


	Chemicals — 7.5%
1,355,000	LSF11 A5 HoldCo LLC, 6.625%, 10/15/29 (144A)	$ 1,317,927
EUR 885,000	Lune Holdings S.a.r.l., 5.625%, 11/15/28 (144A)	863,584

SEC Form N-CSRS filed by Pioneer High Income Fund Inc.