Sweden forward Zlatan Ibrahimovic scored both goals after coming off the bench to secure the nerazzurri’s 16th Scudetto crown.
AS Roma’s hopes of snatching the title on the last day of the season faltered as they were held to a 1-1 draw at Catania, but Ibrahimovic’s double rendered their result meaningless anyway.
Fiorentina claimed the last Champions League qualifying position after finishing fourth following their 1-0 win at Torino.
Juventus had already made sure of third place.
AC Milan missed out and will play in the UEFA Cup next season after finishing fifth despite a 4-1 home win over Udinese.
Parma and Empoli went down to Serie B with the already relegated Livrono while Catania’s point was enough for the Sicilians to survive the drop.
Inter may have won the title but at half-time things seemed to be going against them and they looked like living up to their reputation as chokers.
Roma needed to win to keep their hopes alive and took the lead after just eight minutes courtesy of a stunning goal from Montenegro forward Mirko Vucinic.
He took the ball from out on the right flank, beat three men with a combination of skill and pace and then fired a cross shot past Albano Bizarri and just inside the far post.
Inter now had to win to keep hold of their title but they struggled under the heavy rain during the first half.
Coach Roberto Mancini responded to the situation early in the second period by throwing on Ibrahimovic in a three-pronged attack alongside Julio Cruz and Mario Balotelli.
The Swede had not played since March 29th in a 2-1 home defeat to Juventus but he quickly adapted to the pace of the game and needed just 11 minutes on the pitch before making the difference.
He took a square pass from Dejan Stankovic in his stride, took two more steps and fizzed a low shot from 20 yards along the slippery surface and past Nicola Pavarini.
And 11 minutes from time, having just had a one-on-one opportunity thwarted by Pavarini, Ibrahimovic met a deep right-wing cross from Brazilian full-back Maicon on the volley to ease Inter’s nerves.
In Sicily, where Catania needed a point to survive the drop, Roma could not quite hold on and Jorge Martinez levelled matters late on ensure Roma’s title wait will go on for another year.
Inter finished the season with 85 points, three more than Roma, whose valiant late charge ultimately came to nothing.