1860 Munich forward Ivica Olic has been suspended for two games and fined £18,000 for gambling on matches, including in the league he plays in.
The German Football Association (DFB) said there was "no evidence of betting manipulation" and the 37-year-old had not bet on his own side's matches.
But its rules do not allow players to gamble, or use a third party to do so.
The DFB said the bets, made between 26 August and 11 September, included nine on games in the German second division.
It said the sums wagered were "almost all three figures" and had been placed with an internet betting company.
"Of course that was a big mistake," Olic said in a statement released through his club.
"It was not about large sums of money, but simply to have fun. I'm very sorry for what has happened."
In the same statement, 1860 Munich said they would "respond accordingly" to the ruling by also imposing "a large fine".
Olic, Croatia's fourth most-capped player, joined the Bundesliga 2 club on a one-year deal in July after leaving Hamburg.
He is currently sidelined after picking up a knee injury in a 2-0 defeat by Wurzburger Kickers on 2 October - a result that leaves his side 14th in the table, fourth from bottom.