During preproduction, as the filmmakers tried to find a good location to shoot the fight, they met with constant obstacles - every suitable arena was booked out. Sylvester Stallone knew that HBO had an upcoming PPV event with Bernard Hopkins taking on Jermaine Taylor in the main event, at the Mandalay Resort and Casino in Las Vegas. Stallone suggested that the film could piggyback the real event, using the real HBO format, the real crowd, even the real press conference setup. As such, the press conference scene was shot only moments after the real press conference with Hopkins and Taylor, whilst the scene when Rocky walks through the curtain and down to the ring was shot using the real Hopkins/Taylor crowd. Stallone was hoping that the crowd wouldn't boo or cause any problems, but as he made his way to the ring (as Rocky), the whole building gave him a standing ovation and began to chant 'ROCKY, ROCKY'. The crowd was never told to stand up or to chant - they had done it completely on their own, and according to the filmmakers, by far the biggest cheer of the night was for Rocky, not for any of the real fighters.
Pedro Lovell reprises his role as Spider Rico, the boxer defeated by Rocky in the opening scene of Rocky (1976).
According to Sylvester Stallone, the shot of Rocky standing alone on the museum steps before the second set of end credits was actually filmed without him knowing.
The film contains flashbacks from every Rocky film in the franchise.
The film was shot in 38 days. The very first thing to be shot was the fight between Dixon and Rocky. This was done because Sylvester Stallone's training (which had been going on for six months) had to stop once the film went into production and he began to concentrate on directing. If the fight had been left until the end of the schedule, Stallone would not have been in as good shape as he was at the start.