Gordon-Levitt, 34, who plays the titular character in the biographical political thriller, said he went to Russia, "wanting to understand this person that I was going to play, observing both his strengths and his weaknesses," reported Entertainment Weekly.
The actor had a four-hour conversation with Snowden, which he was discouraged from recording.
Gordon-Levitt said he wanted people to decide for themeselves whether Snowden is a national hero or a traitor.
"That's really for people to decide on their own, and I would encourage anybody to decide that on their own. I don't want to be the actor guy who's like, 'You should listen to me! What he did was right!' I don't think that's my place. Even though that is what I believe - that what he did was right," he said.