Born in Vienna, Austria-Hungary, he was the son of actor and operetta singer Sigmund Natzler (1862-1913). As a young man he performed at second-rate Vienna theatres and from the 1930s in several cabarets in Paris. After World War II he worked for the German language Service of the BBC.

Nalder is perhaps best remembered for his roles as an Assassin in Alfred Hitchcock's 1956 remake of The Man Who Knew Too Much, the vampire Barlow in the 1979 filmed version of Stephen King's 'Salem's Lot, and the Andorian ambassador Shras in the Star Trek episode "Journey to Babel".

Nalder appeared (at the request of star Frank Sinatra) in a brief, uncredited role as a communist spymaster in John Frankenheimer's 1962 film The Manchurian Candidate. He also had a brief role in the 1981 Walt Disney film The Devil and Max Devlin. In an interview, Nalder claimed that he could not stand working with Bill Cosby, the star of the film. He described him as "a pig", as well as "rude, arrogant, and very untalented."

Nalder's television work also included episodes of the series 77 Sunset Strip, It Takes A Thief, Surfside Six, Boris Karloff's Thriller ("The Terror In Teakwood" and "The Return Of Andrew Bentley"), McCloud and I Spy. In 1979, Nalder appeared as Kurt Barlow in the TV adaptation of the Stephen King novel Salem's Lot. Nalder was also credited as "Detlef Van Berg" in the X rated films Dracula Sucks (1978) and Blue Ice (1985).

Nalder died of bone cancer in Santa Monica, California in 1991, aged 84.