Growing up in the Northwest Terrorities of Canada, Nielsen found a career in acting after having been a radio announcer and disc jockey.

He first came to prominence in the 1956 science fiction movie Forbidden Planet - during the 1950s and 1960s he also starred or guest starred in many television series including Dr Kildare, the Man from U.N.C.L.E. and Hawaii Five-O.

During the 1970s appearances in (mainly) non-recurring roles on television kept Nielsen in work. Appearing in series such as Columbo, Night Gallery, Kung Fu and Fantasy Island (which of course starred Ricardo Montalban). In most cases Nielsen was working in dramatic and serious roles.

During the next few years Nielsen would alternate between serious roles in movies such as Creepshow, Prom Night and television shows such as Murder She Wrote and Father Dowling Mysteries, as well as more comedy roles such as the Police Squad television series, appearances in the Golden Girls and Due South.

With the reprisal of the Frank Drebin character created in the Police Squad television series appearing in the first Naked Gun movie, Nielsen had created a character and persona that he would be able to portray for the next decade.

As well as portraying Lt. Frank Drebin in the remaining Naked Gun movies, he also starred in the Mr Magoo feature film (playing the title character), the Mel Brooks Dracula: Dead and Loving It (again as the title character), as well as the lead roles in other comedy movies such as Spy Hard and Repossessed.

Now in his 70s, Nielsen has understandably slowed down a little. Having played the President in Scary Movie 3, Nielsen is still lending his vocal talents to animated features.