- Lautaro Martínez (77', 90')
- Robin Gosens (83')
- Felipe Anderson (30')
The result means leaders Napoli, on 78 points, can seal the title, their first in 33 years, with a win against Salernitana later on Sunday with six games remaining after this weekend.
Inter dominated possession at the San Siro and thought they took the lead in the 25th minute through Henrikh Mkhitaryan's first-touch strike but Joaquin Correa was offside when setting him up and the goal was ruled out.
Inter continued to create chances but lost the ball outside their own box in the 30th minute after a Francesco Acerbi error, which Lazio midfielder Anderson used to drill low into the corner, having exchanged passes with Luis Alberto.
However, Inter forward Lautaro slid in between the Lazio defence to equalise in the 77th minute from a Romelu Lukaku cross.
The Belgium forward superbly teed up Gosens for Inter's second from a close range six minutes later and Lautaro added another goal seconds from time in an individual effort.
- Marco Guida