Trailing to a Riccardo Sottil goal, the champions hit back with goals from Matteo Darmian and Edin Dzeko to go ahead.
Nicolas Gonzalez was sent off for dissent late on for Fiorentina, before Ivan Perisic extended Inter’s lead at the death to send Simone Inzaghi’s side top.
Handanovic 7; Skriniar 6, De Vrij 6.5, Bastoni 6; Darmian 6.5 (’65 Dumfries 6), Barella 7 (’70 Vecino 6.5), Brozovic 6.5, Calhanoglu 6 (’83’ Gagliardini 6.5), Perisic 7; Lautaro Martinez 6 (’83 Dimarco N/A), Dzeko 7.5 (’70 Sanchez 6)
Player of the match: Edin Dzeko
The Bosnia international has set about filling the void left by Romelu Lukaku and was at his physical best tonight, holding the ball up well and powering Inter ahead with a strong header from a corner. The ex-Roma striker is becoming an important focal point for the team and is growing in form.