The actor posted a photo on Instagram showing him and co-star Michael B. Jordan in the boxing ring rehearsing a move, captioned: "Get ready to go for it!"
The film sees Stallone reprise his famous role as boxer Rocky Balboa and Jordan play Adonis Creed, the grandson of former heavyweight champion Apollo.
After Adonis finds that he has a natural talent for boxing, he tracks down Rocky and asks him to become his trainer and mentor.
Creed is directed and written by Ryan Coogler and will also star Graham McTavish, Tessa Thompson and Phylicia Rashad.
The film is currently scheduled for a November 2015 release in the US, with international release dates unknown.
Coogler has praised Stallone for his acting and writing skills and said that he could not have worked on a Rocky spin-off without his involvement.
"Rocky isn't the main character in the story, but he's a major supporting player," he said. "And nobody knows that character like him; in the few meetings that I've had with him, sometimes he'll talk like Rocky.
"We'll be talking about a scene, and he'll kind of go into acting mode. It's unnerving how good of an actor Stallone is - if I can get Stallone and Mike together in the same frame, the camera might explode."
Reporter & Sub-Editor, Digital Spy Susannah is a freelance writer and sub-editor, specialising in the entertainment industry. She graduated in 2014, with a BA in English and American Literature and Creative Writing, and an MA in Creative Producing. She’s been writing for Digital Spy ever since, after first getting involved through work experience, and has written hundreds of stories for the site on a range of topics, from The Sims to Doctor Who. Susannah has also written for Reveal Magazine. Her special interests are soaps (her Mastermind subject would be 2000s Coronation Street), Marvel and Star Wars. She can also quote far too many lines from Friends and Brooklyn Nine-Nine.
