His family confirmed that Mendelson died on December 25 of congestive heart failure, following a battle with lung cancer. He was 86.
Mendelson's first television special was a documentary about San Francisco Giants hero Willie Mays called A Man Named Mays. He joked that he went from the world's greatest baseball player to the world's worst — Charlie Brown.
Mendelson began collaborating with Peanuts creator Charles Schulz on a documentary about the comic strip, and in 1965, the pair were asked to create the comic strip's first animated special.
The result was A Charlie Brown Christmas, which has gone on to become a holiday classic.
He hired Vince Guaraldi to compose the music for the special, and Mendelson even wrote the lyrics to the opening song "Christmas Time Is Here" himself.
TV execs initially hated the special, leading Mendelson to claim in 2004, "I really believed, if it hadn't been scheduled for the following week, there's no way they were gonna broadcast that show."
Peanuts wasn't the only comic strip Mendelson turned into a television hit, though. He also produced 12 television specials for Garfield.
Mendelson is survived by his wife Ploenta; children Lynda, Glenn, Jason and Sean; stepson Ken; and eight grandchildren.
The @schulzmuseum would like to recognize the passing of Lee Mendelson who died on December 25th at the age of 86. Lee Mendelson, Charles M. Schulz, and Bill Melendez (L-R) produced fifty television specials and four animated feature films. [📸: R. Smith Kiliper] pic.twitter.com/y5ue9X8rdi— Charles M. Schulz Museum (@SchulzMuseum) December 27, 2019