Brazilian youngster Talisca has been a revelation for Jorge Jesus' side since his close-season move from Bahia, and his eighth goal in just nine Primeira Liga appearances was enough to give them a valuable three points.
Benfica dominated the game - played out in front of a sparse Estadio da Luz crowd - from start to finish, but were unusually wasteful in front of goal.
The champions had to rely on a moment of brilliance on the hour from Talisca to make the breakthrough, as he curled an unstoppable left-footed shot beyond Rio Ave goalkeeper Cassio from 25 yards.
Jesus' men began the game brightly, but Cassio was seemingly in no mood to be beaten.
First, the Brazilian stopper saved from Lima, before Enzo Perez wriggled away from a number of Rio Ave challenges only for his shot to be palmed away.
Lisandro Lopez was next to test Cassio with a header in the 24th minute, but somehow Rio Ave managed to get to half-time still level.
It looked like being one of those nights for Benfica when Nicolas Gaitan - brought on at half-time - shot wildly over from close range immediately after the restart.
But Talisca was on hand to spare his team-mate's blushes with an effort Cassio could do nothing about after 60 minutes.
A tight offside call denied Rio Ave an equaliser completely against the run of play, but anything other than a win for Benfica - who are now unbeaten in their last 39 Primeira Liga home games - would have been a misrepresentation of a completely one-sided affair.
