In 1980, Cain left The Babys to join the rock band Journey, taking Gregg Rolie's place on keyboards.

[5] Cain aided Journey's rise to the top of the charts with his first collaborations on the album Escape, composing and playing the piano on songs such as "Don't Stop Believin'", described by AllMusic as "one of the best opening keyboard riffs in rock".

[6] Perhaps his most notable contribution was as sole author of the Journey ballad "Faithfully", a song about life on the road while in a band.

After suffering a hip injury while hiking in Hawaii that required surgery, in 1998 Steve Perry again left the band.

Journey has continued on with three subsequent lead singers, Steve Augeri from 1998 to 2006, Jeff Scott Soto from 2006 to 2007, and Arnel Pineda from 2007 to the present.

[7] In May 2018, Cain became a published author with the release of his memoir, Don't Stop Believin': The Man, the Band, and the Song That Inspired Generations.

[1] Cain and David Kalmusky designed and built Addiction Sound, a recording studio in Nashville, Tennessee.

[11] In November 2022, Cain performed "Don't Stop Believin'", which he co-wrote, at a party at Donald Trump's Mar-a-Lago estate.

[12] He has received two BMI songwriter awards, both for songs co-written with Steve Perry, "Open Arms" and "Who's Crying Now".