The 32-year-old left-back — a key member of the Croatian team that reached the World Cup final in 2018 — joined Milan from Sampdoria just after the tournament on a two-year deal.
But he failed to make any appearances for the seven-time European champions after being diagnosed with early signs of hypertrophy, a thickening of the heart muscle, shortly after his arrival.
“AC Milan announces the termination by mutual consent of the contract with the defender Ivan Strinic,” the Serie A team said in a statement.
“The club wishes the footballer every success in his future career.”
The defender has been linked with a possible move to Serie A rivals SPAL or Parma.
Strinic, who has 49 caps, played six of Croatia’s seven World Cup games in Russia as they reached final where they lost 4-2 to France.
He started his career with Hadjuk Split in his native Croatia, and also played in France and Ukraine before joining Serie A side Napoli in 2015, and Sampdoria in 2017 and AC Milan in 2018.