Lange won an Oscar for her performance in the film, which also starred Dustin Hoffman.
"I turned it down because I had just finished a film called 'Frances,' which was like this huge dramatic role," Lange said today on "Good Morning America."
She went on, "When Sydney Pollack and Dustin came to me about doing 'Tootsie' I thought, 'Oh, it's so lightweight.' So I would just say [to myself 35 years ago], 'Get over it girl. Just do it.' But it was one of the best decisions I ended up ever making because it's a classic film."
Now, Lange is portraying movie star Joan Crawford in the new FX show, "Feud: Bette & Joan."
The series chronicles the infamous rivalry between legends Crawford and Bette Davis (Susan Sarandon) during the filming of the 1962 thriller, "Whatever Happened to Baby Jane."
Despite their bitterness, Lange believes the actresses would have been friends if Hollywood never pinned them against each other.
"I think naturally there was a lot of competition between them and then when they ended up doing this film together, which is only a small part of our series, for publicity for marketing, for all those things, they were kind of set upon each other and it was more than I think it could have been, or should have been," Lange said.
Asked if she thought Joan Crawford would've been happy with her performance, Lange replied, "I tried to do something as honest from my point of view with all the research that I did and everything and everything I learned about her, so I don't know. Hopefully!"
This was a first-time collaboration for Lange and Sarandon. Lange said the pair worked well together.
"There are a lot of actresses of my generation that I haven't had a chance to work with yet that I'd love to, but Susan and I got along great," she said. "It was a long shoot, but it was interesting work. We had a good time."
"Feud: Bette and Joan" airs Sundays on FX.