Mendoza started playing the guitar at an early age, adopting the bass guitar when he was invited to join a band that needed a player. He played in John Sykes' band Blue Murder, from 1991 until 1993. In 1994, he was recruited into a reformed lineup of Thin Lizzy, also featuring Sykes, with guitarist Scott Gorham, keyboard player Darren Wharton and drummer Brian Downey. After some preliminary one-off concerts, the band toured more consistently from 1996 until 2000, replacing the departing Downey with Tommy Aldridge and releasing the live album One Night Only.
After Sykes left Thin Lizzy in 2009, Mendoza rejoined the band for a third stint, this time with Gorham, Wharton, Downey, singer Ricky Warwick and guitarist Vivian Campbell. This lineup of Thin Lizzy toured Europe throughout 2011, before a US tour at the end of the year, and a further tour of Europe in early 2012.
When not touring, Mendoza has played with his band Mendoza Heredia Neto, featuring drummer Joey Heredia and keyboard player Renato Neto, on Tuesday nights at La Ve Lee Jazz Club in Studio City. The band has recorded a live CD, Live in L.A.
On May 30 2014, it was announced that Mendoza was leaving Black Star Riders at the end of the contemporaneous US tour to work on other projects. Whether or not he will be involved in future reunions of Thin Lizzy remains unclear.
He is currently playing with The Dead Daisies, who have recently released a new album titled The Face I Love and are on tour with Kiss and Def Leppard.
Mendoza spent his formative years living with his grandmother in Tijuana, Mexico. He now lives in California and has five children: Marco Rentería, who is the bass guitarist in the award winning Mexican band Jaguares and who played on Mendoza's solo album Live for Tomorrow; He married his current wife Leah, an administrative professional at a high profiled land development company, on December 2, 2001. Mendoza is a well-known supporter of gun rights. He enjoys hunting, fishing, trapping, and the general outdoors.