His career started in 1985 when he was a cast member of Saturday Night Live till 1990. His career kick started when he was offered a generous $500,000 movie contract. Within two years, he was nominated for an Emmy Awards. Lovitz stepped foot in television series with 1985-86 series Foley Square where he played the role of Mole, an investigator. His voice too is frequently heard in many cartoons and films. He has made special appearances on The Simpsons and lent his voice for Disney animated movie The Brave Little Toaster.

After appearing in several commercials and print ads, Jon was given the starting role as an antagonist in Mom & Dad Save The World. His protagonist character was seen in the movie High School High. He also appeared on Friends twice, as Gary Fogel in Seinfield, on Two and a Half Men and also guest starred twice on Newsradio. He was also seen as the Raw Guest Host on May 2010 on WWE Raw.

Lovitz is also quite attached to theatre. He has appeared in Neil Simon's play The Dinner Party at the Music Box Theatre in Broadway. Being a great singer, he has sang at Carnegie Hall twice, also sang at the U.S. open and at Dodger Stadium. In 2006, Jon was appointed as a spokesperson for the Subway restaurant advertising campaign. He started stand-up comedy very recently. His first show was at the Laugh Factory in Los Angeles in 2003. He also owns a comedy club "The Jon Lovitz Comedy Club at Aubergine" opened in November 2007.

On Universal Studios Hollywood's Universal Citywalk, there is another of Jon's Comedy Club. The club holds record for hosting the first ever MNA Roast stand-up comedy show in 2009. The name was changed to "The Jon Lovitz Comedy Club and Podcast Theatre" on May 29 2011. During a premiere event here, Kevin Smith hosted six podcasts. After some very great shows, the Jon Lovitz Comedy Club was unfortunately closed on November 2014. Though his personal life is private, he is romantically involved with model Janice Dickinson.