Jorge Jesus' men went into the game behind Sporting on goal difference, and failed to put the pressure on their Lisbon neighbours as struggling Arouca earned a shock result at Estadio da Luz.
It was the visitors who took the lead as midfielder David Simao netted his first goal of the season 19 minutes into the game.
Arouca's defence was able to hold out for most of the first half, but Benfica pulled level five minutes before half-time through Rodrigo.
The visitors refused to lie down and got back on course for only a third win of the campaign when attacker Serginho restored their advantage 16 minutes from time.
Arouca's hopes of an unlikely triumph were dashed with seven minutes remaining, Brazilian striker Lima converting from the penalty spot to spare Benfica's blushes following Ivan's foul on substitute Miralem Sulejmani.
