Continuity mistake: The day after the fight in Tijuana, when Donnie's at his desk he's wearing a grey striped tie, but when Donnie walks into his boss' office he's wearing a navy tie with dots. (00:07:30)
Revealing mistake: A man is taking a picture of his family in front of the Rocky Balboa Statue but his disposable camera is facing the wrong way. (00:16:00)
Deliberate mistake: While Donnie is training at Front Street Gym, when Rocky repeats, "One step at a time, one punch at a time, one round at a time," the closeup of two children watching from outside the ring is a flipped shot, note the backwards Nike swoosh logo and Everlast ring rope spacer. (00:53:05)
Continuity mistake: When Donnie goes down during his fight with Conlan, his position on the mat changes between the closeups and the long shot. (01:57:10)
Factual error: When Creed and his girl go to the sandwich shop the cashier tells him it's $10.95. He hands her a $20 and she gives him back a $10 bill. Not only that, there is no way you would get two fully loaded Philly sandwiches and drinks for $10.95 in Philly.
Factual error: The power socket behind Rocky and Adonis in the locker room while they are in London isn't British.
Character mistake: In the final fight at Goodison Park, the commentator says 100,000 people are in attendance. Capacity of Goodison Park is 40,000, and even allowing for people in the "pitch" area around the ring there's nowhere near space for that many, unless there was another layer of fans standing on people's shoulders.