The complaint filed Tuesday in Walla Walla Superior Court says the man suffers anxiety and nightmares. He's seeking an amount of money that would be determined at a trial in the civil rights lawsuit.
The Union-Bulletin reports the man was jailed in August 2011 for investigation of child rape when he was raped three times by cellmate John Markwell.
Markwell was convicted by a jury and, as a persistent offender with a history of violent sex crimes, he is serving a life sentence at the Washington State Penitentiary.
The plaintiff pleaded guilty to the child rape charges and is serving a 10-year sentence at the Monroe Corrections Center.