Sylvester Stallone seriously injured a pectoral muscle during his intensive training for Rocky II. 

When Rocky is seen training, he is sparring with a smaller and quicker fighter. The sparring partner is played by real life Champion Roberto Duran. 

This movie is notable for being the first of three Rocky films that Stallone would not only write and star in, but direct as well.

During the "Beast Aftershave" commercial filming scene, the clapperboard reads "Director: John Pleshette", the real name of the actor playing the director.

The book that Rocky reads to Adrian is Edgar Rice Burrough's "The Deputy Sheriff of Comanche County" which was originally published in 1940.