Sunderland have confirmed "significant investment" from the American consortium FPP Sunderland Limited, although exact figures are undisclosed.
This deal brings no change to the current ownership structure, as chairman Stewart Donald remains the majority and controlling shareholder.
The value of the investment is reported to be around £10m.
There had been previously been speculation surrounding a possible takeover at the League One club.
"FPP Sunderland Limited is backing the current management of Sunderland AFC through a significant investment it has made in the club's holding company, Madrox Partners Ltd," the statement said.
"Other terms of the investment are not being disclosed. The new investment is consistent with Mr.Donald's intention to attract additional financial resources to support the second phase of his plan to regenerate the club, including investing in the club's academy, recruitment structure, stadium infrastructure and fan experience."
Sunderland are currently eighth in League One, three points adrift of the play-off places.