Arnautovic was brought to West Ham by Slaven Bilic last summer, and he initially struggled at the London Stadium.
The Austrian international was criticised for showing a lack of work rate, and not being productive enough in the final third, during his first few months at the London club.
However, since David Moyes has taken charge, Arnautovic has been in outstanding form.
The ex-Stoke City man has become a talismanic figure for the Hammers, and become a vital part of their attacking play.
And Kouyate said: “I love my teammates. Marko [Arnautovic], Arthur Masuaku and Manu [Lanzini] have helped me to get back to my top level.
“Marko is unbelievable, but not only on the pitch but outside the pitch.”
Arnautovic has scored seven goals and made three assists in his last nine Premier League appearances.
Moyes has used Arnautovic in a more central striking role, and he has thrived in the position.
West Ham are next in action when they take on Liverpool in two weekends’ time.