Hanks portrays the movie mogul in the new drama, about the battle to bring Mary Poppins to the big screen, but had to omit scenes that featured the animator puffing on cigarettes in order to satisfy censors.
The actor reveals producers endured protracted negotiations over the issue, but they were prevented from showing Disney smoking onscreen.
Hanks says, "We had a hard enough time trying to have him smoke... If we smoked cigarettes in this movie about Walt Disney making Mary Poppins, it would be rated R (restricted). That's just the way it works. You couldn't believe the negotiations. It came down to us not being able to light a cigarette or inhale a cigarette.
"You do see one big scene where Emma (Thompson) as (Poppins author P.L. Travers) storms into my office and you see me putting out a cigarette in the ashtray on Walt's desk.
"I did always have a pack of cigarettes in my shirt pocket and sometimes I was playing around with them and a cigarette lighter here and there, but I never could smoke one.
"The man smoked three packs of cigarettes a day. People who knew Walt say that you could always hear him coming down the hall, because you'd hear him coughing from smoking all those cigarettes."
Disney died of lung cancer in 1966 at the age of 65.