Exhibit 99.1

BlackRock Kelso Capital Corporation Declares Regular Quarterly Distribution of $0.21 per Share,

Announces March 31, 2014 Quarterly Financial Results

New York, New York, May 1, 2014 - BlackRock Kelso Capital Corporation (NASDAQ:BKCC) (“BlackRock Kelso Capital” or the “Company”, “we”, “us” or “our”) announced today that its Board of Directors has declared a quarterly distribution of $0.21 per share payable on July 2, 2014 to stockholders of record as of June 18, 2014.

HIGHLIGHTS:

Operating Results for the Quarter Ended March 31, 2014:

Net investment income per share: $0.15

Distributions declared per share: $0.26

Earnings per share: $0.31

Net asset value per share: $9.59

Net investment income: $11.1 million

Net realized and unrealized gains: $11.8 million

Net increase in net assets from operations: $22.9 million

Net investment income per share, as adjusted¹: $0.19

Net investment income, as adjusted¹: $14.3 million

Earnings per share, as adjusted¹: $0.35

Net increase in net assets from operations, as adjusted¹: $26.1 million

Certain transactions completed during the quarter include:

Portfolio and Investment Activity

(dollar amounts in millions)

2

Liquidity and Capital Resources

As previously announced, on March 27, 2014, we entered into a five year $405.0 million Amended and Restated Senior Secured Revolving Credit Facility (the “Credit Facility”), which amended and restated our revolving credit facility previously outstanding. The Credit Facility has a maturity date of March 27, 2019, includes a ratable amortization in the final year, and represents an increase of $55.0 million in revolving commitments over the prior revolving facility. The interest rate applicable to borrowings is generally LIBOR plus an applicable spread of 2.25%, a .25% reduction from the prior revolving credit facility. The Credit Facility also includes an “accordion” feature that allows us, under certain circumstances, to increase the size of the Credit Facility up to $750.0 million in revolving loan commitments.

At March 31, 2014, we had approximately $34.1 million in cash and cash equivalents, $459.0 million in debt outstanding and, subject to leverage and borrowing base restrictions, $250.0 million available for use under our amended and restated revolving credit facility, which matures in March 2019. Relative to our $1.1 billion dollar portfolio at fair value, we continue to have sufficient debt capacity to deploy in attractive investment opportunities. At March 31, 2014, we were in compliance with regulatory coverage requirements with an asset coverage ratio of 255% and were in compliance with all financial covenants under our debt agreements. In the near term, we expect to meet our liquidity needs through use of the remaining availability under our credit facility, continued cash flows from operations, and through periodic add-on equity and debt offerings, as needed. The primary use of funds will be investments in portfolio companies, reductions in debt outstanding and other general corporate purposes.

Recent Developments

We have entered into a contract to sell our largest equity investment, Electrical Components International, at a price range of $71.5 million to $72.5 million, which is anticipated to produce realized gains of approximately $49.0 million. As anticipated, this would further reduce our portfolio’s equity composition while generating additional proceeds to redeploy into income producing assets.

Conference Call

BlackRock Kelso Capital will host a webcast/teleconference at 4:30 p.m. (Eastern Time) on Thursday May 1, 2014 to discuss its first quarter 2014 financial results. All interested parties are welcome to participate. You can access the teleconference by dialing, from the United States, (800) 374-0176, or from outside the United States, (706) 679-3431, shortly before 4:30 p.m. and referencing the BlackRock Kelso Capital Corporation Conference Call (ID Number 11886655). A live, listen-only webcast will also be available via the investor relations section of www.blackrockkelso.com. Both the teleconference and webcast will be available for replay by 7:30 p.m. on Thursday, May 1, 2014 and ending at midnight on Thursday, May 8, 2014. To access the replay of the teleconference, callers from the United States should dial (855) 859-2056 and callers from outside the United States should dial (404) 537-3406 and enter the Conference ID Number 11886655.

Prior to the webcast/teleconference, an investor presentation that complements the earnings conference call will be posted to BlackRock Kelso Capital’s website within the presentations section of the investor relations page (http://www.blackrockkelso.com/InvestorRelations/Presentations/index.htm).

3

BlackRock Kelso Capital Corporation

Consolidated Statements of Assets and Liabilities

(Unaudited)

4

5

The Company reports its financial results on a GAAP basis; however, management believes that evaluating the Company’s ongoing operating results may be enhanced if investors have additional non-GAAP basis financial measures. Management reviews non-GAAP financial measures to assess ongoing operations and, for the reasons described below, considers them to be effective indicators, for both management and investors, of the Company’s financial performance over time. The Company’s management does not advocate that investors consider such non-GAAP financial measures in isolation from, or as a substitute for, financial information prepared in accordance with GAAP.

The Company records its liability for incentive management fees based on income as it becomes legally obligated to pay them, based on a hypothetical liquidation at the end of each reporting period. The Company’s obligation to pay incentive management fees with respect to any fiscal quarter is based on a formula that reflects the Company’s results over a trailing four-fiscal quarter period ending with the current fiscal quarter. The Company is legally obligated to pay the amount resulting from the formula less any cash payments of incentive management fees during the prior three quarters. The formula’s requirement to reduce the incentive management fee by amounts paid with respect to such fees in the prior three quarters has caused the Company’s incentive management fee expense to become, and currently is expected to be, concentrated in the fourth quarter of each year. Management believes that reflecting incentive management fees throughout the year, as the related investment income is earned, is an effective measure of the Company’s profitability and financial performance that facilitates comparison of current results with historical results and with those of the Company’s peers. The Company’s “as adjusted” results reflect incentive management fees based on the formula the Company utilizes for each trailing four-fiscal quarter period, with the formula applied to the current quarter’s incremental earnings and without any reduction for incentive management fees paid during the prior three quarters. The resulting amount represents an upper limit of each quarter’s incremental incentive management fees that the Company may become legally obligated to pay at the end of the year. Prior year amounts are estimated in the same manner. These estimates represent upper limits because, in any calendar year, subsequent quarters’ investment underperformance could reduce the incentive management fees payable by the Company with respect to prior quarters’ operating results. Similarly, the Company records its liability for incentive management fees based on capital gains by performing a hypothetical liquidation at the end of each reporting period. The accrual of this hypothetical capital gains incentive management fee is required by GAAP, but it should be noted that a fee so calculated and accrued is not due and payable until the end of the measurement period, or every June 30. The incremental incentive management fees disclosed for a given period are not necessarily indicative of actual full year results. Changes in the economic environment, financial markets and other parameters used in determining such estimates could cause actual results to differ and such differences could be material. For a more detailed description of the Company’s incentive management fee, please refer to the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2013 on file with the Securities and Exchange Commission (“SEC”).

Computations for the periods below are derived from the Company’s financial statements as follows:

As Adjusted¹: Amounts are adjusted to remove the incentive management fee expense based on Gains, as required by GAAP, and to include only the incremental incentive management fee expense based on Income. The incremental incentive management fee is based on each trailing four-fiscal quarter period, applied to the current quarter’s incremental earnings, and without any reduction for incentive management fees paid during the prior three quarters. Amounts reflect the Company’s ongoing operating results and reflect the Company’s financial performance over time.

Pre-Incentive Fee²: Amounts are adjusted to remove all incentive management fees. Such fees are calculated but not necessarily due and payable at this time.

6

About BlackRock Kelso Capital Corporation

BlackRock Kelso Capital Corporation is a business development company that provides debt and equity capital to middle-market companies.

The Company’s investment objective is to generate both current income and capital appreciation through debt and equity investments. The Company invests primarily in middle-market companies in the form of senior and junior secured and unsecured debt securities and loans, each of which may include an equity component, and by making direct preferred, common and other equity investments in such companies.

Forward-Looking Statements

This press release, and other statements that BlackRock Kelso Capital may make, may contain forward-looking statements within the meaning of the Private Securities Litigation Reform Act, with respect to BlackRock Kelso Capital’s future financial or business performance, strategies or expectations. Forward-looking statements are typically identified by words or phrases such as “trend,” “potential,” “opportunity,” “pipeline,” “believe,” “comfortable,” “expect,” “anticipate,” “current,” “intention,” “estimate,” “position,” “assume,” “outlook,” “continue,” “remain,” “maintain,” “sustain,” “seek,” “achieve,” and similar expressions, or future or conditional verbs such as “will,” “would,” “should,” “could,” “may” or similar expressions.

BlackRock Kelso Capital cautions that forward-looking statements are subject to numerous assumptions, risks and uncertainties, which change over time. Forward-looking statements speak only as of the date they are made, and BlackRock Kelso Capital assumes no duty to and does not undertake to update forward-looking statements. Actual results could differ materially from those anticipated in forward-looking statements and future results could differ materially from historical performance.

In addition to factors previously disclosed in BlackRock Kelso Capital’s SEC reports and those identified elsewhere in this press release, the following factors, among others, could cause actual results to differ materially from forward-looking statements or historical performance: (1) our future operating results; (2) our business prospects and the prospects of our portfolio companies; (3) the impact of investments that we expect to make; (4) our contractual arrangements and relationships with third parties; (5) the dependence of our future success on the general economy and its impact on the industries in which we invest; (6) the ability of our portfolio companies to achieve their objectives; (7) our expected financings and investments; (8) the adequacy of our cash resources and working capital, including our ability to obtain continued financing on favorable terms; (9) the timing of cash flows, if any, from the operations of our portfolio companies; (10) the impact of increased competition; (11) the ability of our investment advisor to locate suitable investments for us and to monitor and administer our investments; (12) potential conflicts of interest in the allocation of opportunities between us and other investment funds managed by our investment advisor or its affiliates; (13) the ability of our investment advisor to attract and retain highly talented professionals; (14) fluctuations in foreign currency exchange rates; and (15) the impact of changes to tax legislation and, generally, our tax position.

BlackRock Kelso Capital’s Annual Report on Form 10-K for the year ended December 31, 2013 filed with the SEC identifies additional factors that can affect forward-looking statements.

Available Information

BlackRock Kelso Capital’s filings with the SEC, press releases, earnings releases and other financial information are available on its website at www.blackrockkelso.com. The information contained on our website is not a part of this press release.

# # #

7