The Serbian striker hit three times before the break to put the Viola in command, and whilst Artur Ionita pulled one back for Benevento, a late Valentin Eysseric effort sealed the comprehensive win.
The victory sees Fiorentina earn their first win in four, whilst Benevento’s winless streak extends to 11 matches in Serie A.
Fiorentina made a fine start to the match and were ahead in the opening 10 minutes, as Vlahovic took advantage of some slack defending to tuck home a deflected Eysseric cross in the box.
The Viola were dominant and ought to have doubled their advantage moments later as Lucas Martinez Quarta chested down a cross in a crowded box and had the goal at his mercy, but could only scoop over.
Benevento were struggling to make their mark on the match and found themselves two goals down midway through the first half, with Vlahovic earning his brace. A deep Franck Ribery freekick was met by Martin Caceres to force a good save from Lorenzo Montipo, but Vlahovic was on hand to tuck the rebound in.
On the verge of half time Vlahovic netted his hattrick in style, swivelling in possession and forcing space before rifling in from the edge of the box.
Benevento came out fighting in the second half and reduced the deficit early from a corner, with Ionita rising highest to meet Caprari’s delivery.
The latter almost dragged Benevento back into the match with a clever jinking run into the box, but his effort was palmed away by Dragowski.
Any hopes of a fightback were extinguished with a quarter of an hour remaining, as Eysseric met Ribery’s pass across the box and delicately lofted the ball over Montipo.