During an interview with Bad Taste (via Superhero Hype), Mark Ruffalo revealed that the Hulk was in Captain America: Civil War at one point, but he was eventually removed.
“The reason is too great to be revealed in this movie (Civil War). I was in the script but then they removed my character. They don’t want to reveal where is he and why. I don’t even know if Hulk will be back soon.”
The film stars Chris Evans, Robert Downey Jr, Scarlett Johansson, Anthony Mackie, Paul Bettany, Jeremy Renner, Don Cheadle, Elizabeth Olsen, Sebastian Stan, Chadwick Boseman, Emily VanCamp, Daniel Bruhl, Frank Grillo, William Hurt, Paul Rudd and Tom Holland.
Captain America: Civil War picks up where Avengers: Age of Ultron left off, as Steve Rogers leads the new team of Avengers in their continued efforts to safeguard humanity. After another international incident involving the Avengers results in collateral damage, political pressure mounts to install a system of accountability and a governing body to determine when to enlist the services of the team. The new status quo fractures the Avengers while they try to protect the world from a new and nefarious villain.