The actor toured the prison and screened his Johnny Cash biopic before playing a handful of the Cash songs he performed as the country hero in the film.
The humble GLADIATOR star, dressed in Cash's famous all black ensemble, told the 50-plus inmates who caught his tribute show that he hadn't picked up a guitar since the biopic wrapped last year (05) and felt a "little rusty."
But inmates didn't seem to mind as he recalled a famous Cash concert at the California prison, performing the late country icon's standard FOLSOM PRISON BLUES.
He made them laugh when he revealed his co-star Witherspoon had hoped to join him on his prison visit, adding, "I know you guys would probably rather see Reese."
But inmate ERIC BRELAND insists Phoenix's performance was extremely moving and the biopic screening was stirring.
He says, "I was in tears. It really surprised me."