Born in Copenhagen, Denmark to a well-known Danish stage family, Hersholt toured Europe performing with his family when he was young. He then graduated from the Copenhagen Art School. His first two films were made in Germany in 1906. He emigrated to the US in 1913, and the rest of his movies were made in America. Of his total credits, 75 were silent films and 65 were sound films. He is the uncle of former Canadian Deputy Prime Minister Erik Nielsen, whose brother is the actor Leslie Nielsen. He appeared in 140 films and directed four.
Hersholt's best remembered film roles included Marcus Schouler in Erich von Stroheim's 1924 film Greed and Shirley Temple's beloved grandfather in the 1937 film version of the 1880 children's book, Heidi, written by Swiss author Johanna Spyri. During his long career in the movies, his roles ran the gamut from early silent villains to secondary parts in which his mild Danish accent and pleasant voice suited him to depict a succession of benevolent fathers, doctors, professors and European noblemen. Hersholt's last role was in the 1955 movie Run for Cover.
The small-town physician's good humor, innate common sense and scientific training helped drive off a series of villainous types who tried to interfere with the peaceful lifestyle of River's End. Produced by Dorothy McCann, the radio series became a popular long-run hit, continuing on CBS until January 6, 1954, with Hersholt so strongly identified with the role that he received mail asking for medical advice. There were various spin-offs as Hersholt co-wrote a Dr, Christian novel and made a series of six family films as Christian from 1939 to 1941. In 1956, his Dr. Christian character made the transition to television, scripted by Gene Roddenberry, with Macdonald Carey as his nephew Dr. Mark Christian.
In 1939 Hersholt helped form the Motion Picture Relief Fund to support industry employees with medical care when they were down on their luck. The fund was used to create the Motion Picture Country House and Hospital in Woodland Hills, California, and it led to the creation in 1956 of the Jean Hersholt Humanitarian Award, an honorary Academy Award given to an "individual in the motion picture industry whose humanitarian efforts have brought credit to the industry."
Hersholt was honored for his services to the industry twice with an honorary Academy Award, first in 1940 and the second time in 1950. Hersholt died in Hollywood, California and was interred in Forest Lawn Memorial Park Cemetery in Glendale, California. He has a star on the Hollywood Walk of Fame at 6501 Hollywood Boulevard for his work in motion pictures and another one at 6701 Hollywood Boulevard for his work in radio.