Peno has been a member of the junior national teams of Serbia. With the junior national teams of Serbia, he has played at the following tournaments: the 2012 FIBA Europe Under-16 Championship, where he won a bronze medal, the 2013 FIBA Europe Under-16 Championship, where he won a silver medal and was voted to the All-Tournament Team and named MVP, the 2014 FIBA Europe Under-18 Championship, where he won a silver medal, the 2014 FIBA Under-17 World Championship, where he won a bronze medal, the 2015 FIBA Under-19 World Championship, and the 2016 FIBA Europe Under-20 Championship.