The film's villain, Dr. Hasslein, had been briefly mentioned at the beginnings of O Planeta dos Macacos (1968) and De Volta ao Planeta dos Macacos (1970).
With De Volta ao Planeta dos Macacos (1970) doing well at the box office, producer Arthur P. Jacobs sent a telegram to writer Paul Dehn four months after the film's release which simply said: "Apes exist. Sequel required."
In a 2010 interview with the Archive of American Television, Eric Braeden admitted that he did not really like the role of Dr. Otto Hasslein and considered it to be a caricature. Nevertheless, he added that he had a good time making the film as he enjoyed working with Roddy McDowall, Kim Hunter and Don Taylor, whom he described as a very good director.
All five original "Planet of the Apes" movies were #1 at the U.S. box office when released. "Escape from the Planet of the Apes" spent one week as the #1 top grossing film: the week of May 23, 1971 it made $4,294,942.
According to actress Kim Hunter, makeup on the original "O Planeta dos Macacos (1968)" took 4 1/2 hours to apply. By the time the third film was done, the makeup department was able to do it an hour quicker. Kim noted that the latex lacked insulation, so your skin was very heated in warm temperatures, but very cold in cool temperatures. During the course of this movie, which was filmed during winter, Kim's makeup appliance develops a "puffed-up" appearance, possibly the result of some padding underneath to compensate for filming in cool temperatures.