The England international produced a neat finish just five minutes in after pouncing on a deflected effort from Daniel Sturridge
The winger struck after just five minutes of play at Soldier Field in Chicago, finishing coolly after latching onto a deflected strike from Daniel Sturridge.
The Reds were good value for their win, although Olympiakos was inches away from earning a point, with Gevorg Ghazaryan denied by the crossbar early in the second half.
Liverpool's first match of the preseason tournament in the U.S. saw it start well, with a free kick in the fourth minute in a dangerous area, before it took the lead a minute later.
Sturridge's attempt from distance deflected off an Olympiakos defender, and fell fortunately to Sterling, who tucked away past a helpless Balazs Megyeri.
The game began to open up later in the half, with Liverpool producing several fast counterattacks, with new signing Lukas Markovic involved.
Olympiakos had appeals for a penalty waved away in the 35th minute, as Javier Saviola earned a yellow card for simulation inside the area.
Moments later, Markovic showed elements of his class as he danced into the Olympiakos area, only to guide his curling right-footed shot too high for the top-right corner target.
Rodgers swung the changes at halftime, taking out Markovic, fellow signing Emre Can and Jose Enrique, and bringing in Joe Allen, Jack Robinson and Coutinho.
However, it was Olympiakos which should have struck first on return to the Soldier Field playing arena, as Ghazaryan's shot was agonizingly denied by the woodwork.
Andreas Bouchalakis then had a gilt-edged chance to equalize, forcing a turnover deep in Liverpool's defensive third, however he could not control his final touch around goalkeeper Jones as the chance dissipated.