Speaking to MTV at the Golden Globe Awards, Branagh praised star Chris Hemsworth and called the Marvel Studios project "promising".
"We have many miles to go and promises to keep, but so far, so good," he said.
He added: "Everybody's doing very good work and just a lot of it is so promising. Fingers crossed for everybody and everything. [Hemsworth] is a great guy."
Based on the Marvel comic of the same name, Thor tells the story of a Norse warrior whose reckless actions reignite an ancient war and result in his expulsion from the realm of Asgard. Thor later learns that his enemies are plotting an invasion of Earth.
Thor, starring Hemsworth, Tom Hiddleston, Natalie Portman, Anthony Hopkins and Renee Russo, is released worldwide on May 6, 2011 via Paramount Pictures.