The 34-year-old former Coventry City captain last played for Portsmouth before becoming the fifth foreign recruit for ATK after Robbie Keane, Jos? Egas dos Santos Branco, Conor Thomas and Jussi Albert J??skel?inen.
"I am sure his experience of playing top tier leagues in England will help ATK in the forthcoming season. We are already on our way to consolidate our team and the coaching staff is making some worthy choices to form a strong side," team principal owner Sanjiv Goenka said welcoming Baker.
A product of the Liverpool Academy, Baker has scored 97 goals.
"It feels great to sign for a champion side like ATK. I am eager to experience Indian football which is going through some exciting times with ISL gaining popularity," Baker said about the move.
"I have heard about the fans who are passionate about this beautiful game and hopefully I can give them enough reasons to rejoice by the end of the season.