Joseph Westheimer was born in Los Angeles on May 18, 1916. His aunt was a secretary to Warner Bros. producer Bryan Foy, and young Joseph spent a lot of time at the studio with her, where he watched Al Jolson filming The Jazz Singer (1927). At age 15 Westheimer got a job as a studio messenger at Warners, then later moved to the prop department. After graduating as an electrical engineer from the California Institute of Technology, he went back to Warners, this time in the Special Effects Department under renowned cinematographer (and later director) Byron Haskin. Westheimer found his calling in the Effects Dept., and over the next few years designed and developed process screens and rear-projection equipment for the studio.
During World War II he joined the army and was stationed at Hal Roach Studios (jokingly called "Fort Roach") in Culver City, where he photographed Army training and propaganda films. He went back to Warners after the war, but in 1947 moved over to Eagle-Lion Films. Two years later he was hired as head of the Optical Effects and Insert Photography Department at Consolidated Film Industries, a major film laboratory and optical house owned by Herbert J. Yates, head of Republic Pictures.
In 1955 he started The Westheimer Company, specializing in visual and optical effects, and ran it for the next 30 years, building it into one of the most respected and reliable effects houses in the business, being especially noted for its elaborate yet classic titles. The company worked extensively in both films and TV, doing effects for such films as Star Wars: The Empire Strikes Back (1980) and The Glory Guys (1965), and TV shows such as Star Trek (1966), The Twilight Zone (1959), The Big Valley (1965) and Honey West (1965), among others.
He died at 82 years of age on November 6, 1998, after a long illness.