The Owls had already been issued with two winding up orders from HMRC, but it is now hoped the new investment will bring an end to the club’s recent financial issues.
Wednesday chairman Howard Wilkinson told the club’s official site: "I am delighted that a bona fide investor has confirmed their commitment to be long term investors in Sheffield Wednesday. I am equally happy that as a sign of their commitment, the investor will inject some short term working capital into the club.
"We still have a small way to go before we can provide full details as to the longer term future, but I believe this news should act as a calming influence upon all of stakeholders, especially our supporters and playing staff."
A spokesman for the third party investor has said: "We are committed to being long term partners of the fans and other stakeholders of Sheffield Wednesday Football Club.
"When appropriate we will share with fans our longer term aspirations for the club, but for now I ask everybody associated with Sheffield Wednesday to continue getting behind the team and focus on what happens on the pitch."
The identity of the investor is still unknown but is expected to be revealed once the investment has been finalised.