At the age of seventeen, he was discovered by Norman Whitfield of Motown Records. Soon after, he became a regular session player for the famed Hitsville studios. The first recording he ever played on was "Papa was a Rolling Stone" by The Temptations. The song went to #1 on the Pop and Rhythm & Blues charts in 1972. It won a Grammy Award in 1983.
After playing on numerous albums, he became a working studio musician, and when Motown moved offices to California in 1973, they paid for him to move so they could continue using his services as a session guitar player. He soon joined the group Rare Earth and is credited as being co-writer on three songs from the Back to Earth album. After quitting Motown in 1975, Ray Manzarek of The Doors employed Paul to become lead guitarist for his new band Nite City. By their second album, Paul had also become the lead singer and wrote a number of songs on the Album Golden Days Diamond Nights. The band had separated by the release of their second album.
In the late 1970s, Paul formed his own band Paul Warren & Explorer - and was a regular on the Sunset Strip scene playing almost every weekend at either the Roxy, Whiskey a Go Go, the Starwood, and Madame Wongs in China Town - among many others. He was signed by RSO Records and released his failed first solo album One of the Kids in 1980. Later that year, RSO Records folded and Paul Warren found himself unemployed. He began being a guitar player for hire between the years 1981 and 1987, working for such greats and The Ventures, Tina Turner and Prism. He is also credited as producing a number of records in this era.
In 1987, he joined Richard Marx at the beginning of his career soon after the release of Richard's multi-Platinum debut album. Paul was Marx's Musical Director for seven years before leaving in 1994. The day after quitting Richard's band, he went out on the road to work as lead guitarist for the late British singer Joe Cocker. The "Have a Little Faith Tour" lasted eighteen months. In 1996, Warren was employed by Italian singer Eros Ramazzotti. His guitar playing for Eros lasted eleven years before quitting for good in 2005. In the interim, circa 1999, he was employed in between tours with Eros to work as guitarist for Rod Stewart. As of 2016, he had been playing behind Stewart for eleven years. In late 2010, he released his first solo album in over a decade - entitled Round Trip - with his own band. The Paul Warren Project.
Paul joined Cactus in 2017.