With reports this morning suggesting the Holland playmaker was set to join Manchester City, making the tussle for his services a two-way one with Manchester United, Sneijder was always going to be the main attraction and did not disappoint as he scored a wonderful first-half free-kick.
But the goal would not prove to be the winner, as Zlatan Ibrahimovic equalised against his former club, before Kevin-Prince Boateng scored the winner with 22 minutes left.
Inter looked the livelier of the sides, with Dejan Stankovic going close and, in the 21st minute, their pressure told when Sneijder curled home a 25-yard free-kick.
Eto'o worked Christian Abbitati at his near post as Inter looked for a second, while Ibrahimovic nearly levelled when he hit the post with a header.
Milan stepped up the pace in the second half and were able to score on the hour, with Clarence Seedorf forcing his way into the box and Ibrahimovic perfectly poised to convert.
With Inter rocking, Milan took full advantage and took the lead when, after Alexandre Pato's effort had been tipped on to the post by Julio Cesar, Boateng was on hand to convert from close range.