Earlier, Napoli edged past struggling Venezia 1-0 to move level on points with leaders Atalanta.
In Turin, referee Maurizio Mariani called over the two captains to tell them he was stopping play while an appeal over the tannoy at the Allianz Stadium called on fans to cut out racist chants.
The two teams then gathered in the centre circle, before the match resumed.
Broadcaster DAZN reported that Fiorentina fans hurled insults in the direction of their former player Vlahovic, who is Serbian.
Since leaving Fiorentina, his club from 2018 to 2022, Vlahovic, 24, has been targeted by fans of the Viola.
In November 2023, Fiorentina were given a suspended one-match ban for chants directed at three Juventus players, including Vlahovic.
Earlier, Romelu Lukaku wasted a chance to put Napoli ahead in the 37th minute from the penalty spot. His effort was saved by visiting goalkeeper Filip Stankovic.
Giacomo Raspadori scored the only goal after 70 minutes, slotting home a loose ball (79mins) after Venezia failed to clear.
Napoli's third-straight victory brought them level with Atalanta, who drew with Lazio on Saturday, and have a superior goal difference.
"Totalling 41 points after 18 matches, nobody, even the most optimistic, thought we could do it at the start of the season, but we still have to improve, we're a developing team," said Napoli coach Antonio Conte.
Inter Milan, 3-0 winners at Cagliari on Saturday, are third, one point behind the leading duo but with a game in hand.
Napoli can move into sole possession of the lead next weekend when they face Fiorentina, while Atalanta and Inter face each other in the Italian Supercup in Saudi Arabia.
