Travis Watson had 15 points and nine rebounds while five other Hapoel players reached double digits in scoring in a 71-54 victory in Greece.
Olympia scored the first nine points of the game but Hapoel found their rhythm and ended up taking a 20-17 lead by the end of the first quarter.
The contest remained tight for the entire second quarter with Moran Roth's jump shot giving the Israeli team a 33-32 half-time advantage.
Despite the offensive fireworks of Michael King, who hit six three-pointers and had a game-high 25, Hapoel took control.
Leading 41-40 after two Sven Schultze free throws for Olympia, Hapoel outscored the Greek outfit 14-4 over the last 5:43 of the third quarter to lead 55-44 and stayed on top the rest of the way.
Hapoel are now 1-1 in Group E while Olympia are 0-2.