Tyrone Treasure poured in 16 points and Benjamin Mockford added 15 points as Great Britain grabbed their first victory of the U20 European Championship Men Division B by knocking off Portugal 62-56 in the classification round Group H.
Great Britain was the only team at the competition which had not yet won a game.
Richard Grznar poured in 32 points and Peter Dorazil collected 10 points and 11 rebounds as Slovakia took the early lead in classification Group I with a 94-80 victory over Hungary.
The Hungarians were led by Mate Medve's 20 points.
In Group G, Norway knocked off Switzerland 78-74 with Nicolai Oestbye scoring 24 points and Stian Mjoes chipping in 11 points and nine assists.