Bojan Ratkovic made the go-ahead lay-up with 13 seconds remaining in overtime as Montenegro edged hosts Bosnia-Herzegovina 90-87 at the U16 European Championship Division B in Sarajevo.
Mladen Novakovic scored 25 points and blocked four shots for the Montenegrins.
Also in Group B, the Netherlands won 61-58 and Denmark suffered a 92-68 mauling against Austria.
In Group A, Germany rolled to their third successive victory, beating Luxembourg 100-39.
Belgium thrashed Slovakia 81-51 and Estonia held on to beat Belarus 74-67.
Bulgaria and Slovenia are off to perfect 3-0 starts in Group C.
The Bulgarians got 26 points from Pavlin Ivanov and held on to beat Switzerland 67-61 while Aljaz Korosec scored 17 as Slovenia beat Romania 91-64.
England clinched their first victory with a 78-48 triumph over Cyprus.
In Group D, Sweden destroyed Ireland 80-48 for their third successive win and Finland defeated FYR Macedonia 86-61.