The 24-year-old Taarabt was presented on Wednesday by club vice-president Adriano Galliani and is eager to make the desired impact at Milan.
"This is a big change for me," Taarabt said. "I have played in important clubs but none like Milan.
"Tottenham, QPR and Fulham are good clubs but not as organised and as professional as Milan.
"This is the great challenge in my career and I cannot wait to prove my quality on the pitch."