Bankrupt Japanese firm MtGox said in a filing that it has found 200,000 lost bitcoins.
The firm said it found the bitcoins - worth around $116m (£70m) - in an old digital wallet from 2011.
That brings the total number of bitcoins the firm lost down to 650,000 from 850,000.
MtGox, formerly the world's largest bitcoin exchange, filed for bankruptcy in February, after it said it lost thousands of bitcoins to hackers.
"MtGox had certain old-format wallets which were used in the past and which, MtGox thought, no longer held any bitcoins," said Mt Gox chief executive Mark Karpeles in the filing.
However, "on March 7, 2014, MtGox confirmed that an old-format wallet which was used prior to June 2011 held a balance of approximately 200,000 bitcoins," he said.
Mr Karpeles said the firm moved the found bitcoins to offline wallets on 14 and 15 March so that they could not be targeted.
At the time of the MtGox theft, about 750,000 customer bitcoins were stolen as well as close to 100,000 of MtGox's own bitcoins.
That amounts to about 7% of all the bitcoins in existence.
MtGox recently won brief bankruptcy protection in the US as the firm's case works its way through Japanese courts.