The walker was used on the planet Kashyyyk, to more effectively deal with the continued Wookiee insurgency. They were used alongside AT-AP artillery in devastating attacks on the massive Wookiee tree cities.
Ozzik Sturn, an Imperial captain based on Kashyyyk with the orders of "protecting" (a.k.a. trapping) Princess Leia Organa to keep Bail Organa from revolting against the Empire, and an avid game hunter, made use of a self-modified AT-KT walker when he was governing the Imperial base on the Wookiee homeworld. He was killed and the walker was destroyed by Galen Marek during his mission to the jungle world.