Under Sheringham, the defending champions suffered four losses and drew thrice in 10 outings to slip to eighth place in the 10-team standings.
"Sheringham is no more the coach. Westwood has taken over as interim coach and will interact with the media today. I will speak to (CEO) Raghu (Iyer) and we will shortly make an announcement," ATK co-owner Utsav Parekh told PTI.
Sheringham, a former Manchester United and Tottenham Hotspur striker, was named the coach of ATK in July last year.
Westwood had guided Bengaluru FC to two I-League titles (2013-14 and 2015-16) in three seasons after taking over the coaching stint in 2013.