The 41-year-old plays new secret agent Aaron Cross in the film, which is directed by Tony Gilroy after Paul Greengrass walked away from the franchise, reported Contactmusic.
Damon had proved a huge success in a trilogy that has grossed nearly USD 1 billion worldwide.
"It was a yes before I even got the script, creatively, even though I didn't know what the heck it was. I always knew it wasn't Jason Bourne so it was something to consider. It was an instant 'no' if that was the case. Who wants to do that? Matt will always be Bourne," he said.
"The Bourne Legacy" also stars Ed Norton and Rachel Weisz.