Swiss businessman Hans-Dieter Cleven claims he is owed 40 million Swiss francs ($41.4 million, 36.5 million euros) by Becker but did not reveal the origin of the sum.
"After the recent decision by a court in London to declare Boris Becker bankrupt was made public, the former business partner of Boris Becker, entrepreneur Hans-Dieter Cleven felt obliged to enforce his demands in light of that procedure," law firm GHM Partners acting for Cleven said in a statement.
Becker -- who won six Grand Slams in the 1980s and '90s; three Wimbledon, two Australian Open and one US Open title -- has denied he is bankrupt and told the German press he can meet all his obligations.
The 49-year-old is currently working as a television pundit during the Wimbledon championship in London.