When Raymond Burr was approached to reprise the role of Perry Mason, he agreed to do so only if Barbara Hale came back as Della Street.
Barbara Hale and Raymond Burr were the only members of the original cast of the series who were still alive at the time the movie was filmed. However, Richard Anderson was a recurring cast member in the series' final season.
In one scene where Paul Drake Jr. is talking to Della in his office, a black and white portrait photo can be seen. Though it is a bit blurred, you can see it is William Hopper who played the original Paul Drake in the older TV series.
William Katt is Barbara Hale's real-life son and this is the first appearance on Perry Mason series of William Katt as Paul Drake, Jr.
Barbara Hale was recovering from a broken hip during filming, which can explain why there are a lot of scenes with Hale sitting down. A stand-in was used for scenes that required Hale to actually walk.