Kevin De Bruyne gave Chelsea a deserved lead in the first half before summer signing Andre Schurrle finished Milan off with a stunning volley in second-half additional time.
Milan shaded the possession in the opening half but Chelsea, with De Bruyne, Eden Hazard and Oscar at the forefront, hit the Italians consistently on the counter, creating several dangerous attacks.
Chelsea made seven changes at half-time and while Milan enjoyed large amounts possession in attacking areas, Jose Mourinho's men defended valiantly and prevented the Italians from getting back into the game.
An unlikely source nearly secured Chelsea an early lead with Branislav Ivanovic back-heeling De Bruyne's cross into the body of Milan keeper Christian Abbiati before flashing a header wide from Oscar's free kick.
Milan created their first chance after 14 minutes as the skilful Stephan El Shaarawy split the Chelsea defence but Kevin Prince-Boateng could only cut inside and fire into the stands.
With Mario Balotelli ineffective and frustrated at the point of attack, El Shaarawy ran the show and his delightful chip into the area was well controlled by Sulley Muntari, whose poke towards goal was parried by Petr Cech and cleared by Ivanovic.
Mourinho's side absorbed the Milan possession and then sprung counter-attacks with a Belgian combination securing the opener as Hazard slipped through De Bruyne, who easily sent Abbiati the wrong way in the 29th minute.
Milan looked much more dangerous in the second half after the introduction of M'Baye Niang and if it was not for desperate defending, the Frenchman could have found the equaliser on several occasions.
Substitute Victor Moses was lively for Chelsea in the second half but continued to waste opportunities when he found himself with space on the right before redeeming himself in the latter stages.
As the players tired, the game became end-to-end with Fernando Torres getting on the end of a number of passes in dangerous areas but either failed to get a shot on target or mis-placed the pass to a team-mate in a scoring position.
Schurrle, who came on in the 69th minute, missed two golden chances before his sweet volley from Moses' cross sealed the contest.
With Chelsea moving to the final to meet Real Madrid at the Sun Life Stadium on Wednesday, Milan will front up in the match before against the Los Angeles Galaxy to decide who finishes third in the tournament.