The Sports Illustrated swimsuit model will appear alongside Adam Sandler and Jennifer Aniston in the Columbia Pictures romantic comedy.
The film is produced through Sandler's Happy Madison production company and was co-written by Allan Loeb, Tim Dowling, Tim Herlihy and Adam Sandler, though details of the plot have not been revealed.
I Now Pronounce You Chuck & Larry director Dennis Dugan will head the project.
Decker's role in the film marks the first for the model, who is married to tennis player Andy Roddick.
Just Go With It begins filming in Los Angeles next month and is due for release over Valentine's Day weekend next year.