In the late 1970s, he started in a band called "Empty Sky," a rock band with hints of jazz. The band was based out of Brooklyn and was one of the biggest up-and-coming young bands. James was the lead singer and bass guitarist. The band consisted of Robert Littera at lead guitar, Julie Pontecorvo on Trumpet, Marco Lagana on trombone, Frank Bonanno on tenor saxophone, Oscar Olivera on drums, Vincent Chirico on rhythm guitar and John Buccellato on electric piano. The band broke up as the members began to mature and take their separate career paths.
He played bass with Clockwork, his first original hard rock band in 1980 to 1983. He then went on to play in the band Rondinelli with Ray Gillen before joining White Lion in 1984.
He played bass with White Lion from 1984 to 1991, and then went on with White Lion drummer Greg D'Angelo to play with former Kiss guitarist Ace Frehley, and then later with Zakk Wylde's side-project Lynyrd Skynhead who evolved into Pride & Glory and released one album in 1994. Although he left the band during their 1994 tour, he returned to play on Zakk Wylde's 1996 solo album Book of Shadows. He had a brief stint in the recording studio with Ozzy Osbourne in 1994 but the sessions were not used, and Ozzmosis was re-recorded by different musicians the next year. In 1995, James, along with Pride & Glory drummer Brian Tichy joined Slash's Snakepit as touring musicians.He was a member of David Lee Roth's band in the late 1990s and early 2000s and performed on his album Diamond Dave.
In 2004, LoMenzo rejoined Zakk Wylde in his band Black Label Society until October 2005 when he was replaced by Black Label Society's original bassist John DeServio.
From February 10, 2006 up until February 8, 2010, LoMenzo was the bassist of thrash metal band Megadeth. The first Megadeth record he performed on was 2007's United Abominations. LoMenzo also performed on the band's next album, Endgame from 2009. On February 8, 2010, it was announced that original Megadeth bassist Dave Ellefson replaced LoMenzo.
In 2010 he played bass for Lynch Mob. James is also part of the band "Hideous Sun Demons." James played bass on the album "Get Your Rock On" by X-Drive which was released August 25, 2014 on Frontiers Records which was produced by the legendary late Led Zeppelin engineer Andy Johns. He is also featured on the upcoming Sweet & Lynch album, "Only To Rise" featuring Michael Sweet, George Lynch, and Brian Tichy due out on Frontiers Records (January 27, 2015).
In October, 2013, he joined former Creedence member, John Fogerty's band.
LoMenzo is also a graphic artist and did the art work for Gilby Clarke's solo album Rubber in 1998. Also, in 1997, he did the photos in Mike Tramp's first solo album Capricorn. LoMenzo is also a member of a tribute band called HAIL!. HAIL!'s rotating cast of members include Andreas Kisser, Tim "Ripper" Owens, Paul Bostaph, David Ellefson, Mike Portnoy, Jimmy DeGrasso and Roy Mayorga. Ripper, DeGrasso, Ellefson and Kisser formed the band in late 2008. The band, toured Europe in 2009 and in June 2010 HAIL! is on their second European tour with the following line-up: Andreas Kisser, Tim "Ripper" Owens, Paul Bostaph and James LoMenzo. Due to the death of previously announced Slipknot bassist Paul Gray, LoMenzo agreed on only one day’s notice to fly to Portugal and play the Rock In Rio Festival where HAIL! was scheduled to perform on May 30, 2010. Lomenzo also joined Lynch Mob in late July 2010, replacing Marco Mendoza. James previously jammed with Lynch Mob drummer Brian Tichy in both Pride & Glory and Slash's Snakepit.
On August 29, 2012, LoMenzo was announced as a cast member of The Amazing Race 21 along with his partner Mark "Abba" Abbattista. They ended up in 6th place out of 11 teams and were the sixth team eliminated at Sokolniki Park in Moscow, Russia due to an unsuccessful search for Abba's stolen passport.
In October 2014, LoMenzo joined former Megadeth members Nick Menza and Chris Poland for a yet unnamed project, they have already started to record an EP with six songs confirmed to be in writing process and will be released early 2015.
James LoMenzo is best known for his frequent use of the Warwick Buzzard bass and Warwick Stryker bass. His amplification section is dominated by Ashdown amps and cabinets. His effects pedals include Dunlop Crybaby, MXR Chorus, MXR Distortion, and Aphex Punch as well as other pedals. He has his own signature pedal, the Ashdown Lomenzo Hyperdrive. Interestingly, his rig bears a strong resemblance to that of John Entwistle, who also used Ashdown amps and Buzzard basses (which he designed himself). LoMenzo's live rig can be seen here. He is an endorser of RotoSound bass strings. He is also known to play a spyder model Alembic bass guitar. He was also seen playing a Fender Marcus Miller Jazz Bass for the entirety of the 2007 Megadeth Tour of Duty. As of September 2008, James has been seen playing a Yamaha BB Custom Shop model; which in itself, has a slightly smaller body than a standard BB, two pairs of P bass pick-ups (one reversed), a neck pick-up based on a Gibson Model One, a maple neck and a Hipshot D-Tuner. Some Megadeth photos show LoMenzo playing Yamaha Attitude Ltd models that also have the P-bass/neck pickup and D-tuner configuration.With Rondinelli
Wardance (Recorded circa 1985, released 1996)
With White Lion
Big Game (1989)
Mane Attraction (1991)
The Best of White Lion (1992)
With Pride & Glory
Pride & Glory (1994)
With Zakk Wylde
Book of Shadows (1996)
With Mike Tramp
With David Lee Roth
Diamond Dave (2003)
With Hideous Sun Demons
Hideous Sun Demons (2004)
With Black Label Society
Hangover Music Vol. VI (2004)
United Abominations (2007)
With Tim "Ripper" Owens
Play My Game (2009)
Get Your Rock On (2014)