Deutsche Bank Skyliners threw a real scare into Besiktas in Istanbul on Tuesday but the Turkish side ultimately prevailed 84-76 to earn a place in the Eurocup.
Besiktas had claimed a seven-point win in the opening leg in Germany last week and returned home looking to close out the victory.
Late in the first half, it seemed Besiktas would easily progress when a Michael Ignerski three-point play gave them a 38-26 lead on the night and a 19-point advantage on aggregate.
Cevher Ozer had eight points and Ignerski seven at that juncture.
The Skyliners found a new gear.
A basket from Ajene Moye with 4:40 to go in the third quarter and three-balls from Moye and Pascal Roller triggered an 18-3 run for the visitors.
That left them with a 58-51 lead in the game and tied the game on aggregate with less than a minute remaining in the frame.
Bekir Yarangume stopped the bleeding for Besiktas.
He nailed a jumper, reducing the German team's lead to 58-53 at the end of the third.
That basket also sparked a 17-2 game-winning surge, during which Mire Chatman scoring seven of his team-high 17 points.
Besiktas won by 15 points on aggregate.
Besiktas' Andrew Ogilvy finished with 16 points, Yarangume 13 and Cuneyt Erden 12.
For the Skyliners, Moye had a game-high 20 points in defeat with Jimmy McKinney contributing 17, Jermaine Bucknor 14 and Dashaun Wood 12.