Former Brazil manager Dunga has instructed lawyers to recover a £750,000 loan he claims he made to QPR in 2006.
Dunga, who also captained Brazil to World Cup glory in 1994, has previously been acknowledged by QPR as an investor in the club, when it was under previous owners.
He has instructed lawyers Collyer Bristow to pursue his claim in the High Court if necessary, and hopes the current owners of the club, who include Flavio Briatore and Bernie Ecclestone, agree to repay his loan.
The 47-year-old said in a statement released by his lawyers: "I loaned my money to QPR in good faith when they needed it and am very disappointed that the new owners, who are very wealthy, are now refusing to pay it back. I am fully confident in the English system of justice and that the court will help me recover my loans."
Steven Heffer, of Collyer Bristow, said: "I can confirm I have been instructed by Carlos Dunga to issue proceedings in the High Court to recover the money he lent to QPR.
"I am waiting to hear back from QPR's lawyers whether the loan will be repaid without the need for a court action. It would be inappropriate to say anything further at this stage."
QPR were offering no comment.