The 38-year-old former Swedish international last played for MLS side Los Angeles Galaxy in October.
Ibrahimovic has signed a six-month contract worth 3.5 million euros ($3.9 million) with the option for an additional season with the struggling Italian side.
Polish striker Krzysztof Piatek will start ahead of the former Manchester United and Paris Saint-Germain player at the San Siro in the match against 17th-placed Sampdoria.
Former European champions AC Milan are 12th in the Serie A table, 14 points off the Champions League berths.
Ibrahimovic helped Milan win their last Serie A title in 2011 but left the club eight years ago for PSG.