An active live performer, Leitham has been bassist on more than 125 recordings including ten of her own. She is known for long associations with Mel Torme and Doc Severinsen. She has also appeared with Woody Herman, George Shearing, Gerry Mulligan, Peggy Lee, Joe Pass, Cleo Laine, Louis Bellson, Pete Rugolo, Bill Watrous and been a member of The Tonight Show All-Stars, The Woody Herman Thundering Herd, the Benny Carter Quintet, and the Bob Cooper Quartet.
Leitham has performed as a featured artist or group member at major jazz festivals in North America and internationally. and has been a presenter at workshops and clinics in the U.S. She has performed clinics and master classes at many major universities and was jazz bass instructor at CSULB. She has been a featured artist at many of the world’s most prestigious jazz festivals and clubs. She has appeared with her trio at some of the finest venues in the world, including the Blue Note, Iridium, Smalls, and Dizzy’s Club Coca-Cola in New York, The Toronto Pride Fest,also festivals in France and The Netherlands, Hungary and Japan, Mammoth Lakes and Sweet and Hot Jazz Festivals in California, Blues Alley in Washington, DC, Catalina's, Blue Whale, The Jazz Bakery, The Lighthouse, Donte's. Carmello's, Alphonse's, and Cafe 322 in Los Angeles, Shanghai Jazz, the Deer Head Inn in the Delaware Water Gap and a host of others.
Leitham own recordings include Leitham Up, The Southpaw, Lefty Leaps In, Live! and Two for the Road (a duo with guitarist Jimmy Bruno). Her 2006 release, The Real Me, features her original compositions and arrangements and, for the first time, her singing voice. Additionally 2008's critically acclaimed "Left Coast Story", the 2011 release of a live DVD "The Real Me Live", her 2014 release "Future Christmas", and her 2015 release "MOOD(S)WINGS".
In 2001 Leitham transitioned from being known as John Leitham Leitham is the subject of an award-winning documentary, "I Stand Corrected". It premiered and won the best film award at the American Documentary Film Festival in April, 2012.
- Gary W. Kennedy. "John Leitham". In Deane L. Root. Grove Music Online. Oxford Music Online. Oxford University Press. (subscription required)
- Lynell George, Going solo in a man's world, Los Angeles Times, August 31, 2003
- The music is sweeter now that Jennifer is not John, Hollywood Reporter, October 2, 2006