The two men were employees of Able Building and Maintenance Company, a San Francisco-based business that provides contract services for the college, police said.
They were in an office at the college at about 2 a.m. drinking alcohol when one man allegedly sodomized the other man, police said.
The victim, a 32-year-old man, reported the assault to police shortly after 3 a.m. Tuesday. He was examined and treated at Contra Costa Regional Medical Center, police said.
His attacker was identified as Ulises Pedro Araujo, a 38-year-old Richmond man.
Araujo was arrested at about 10:30 p.m. Tuesday and booked into county jail in Martinez on suspicion of sodomy with force and false imprisonment, according to county jail records.
He also has a no-bail immigration hold.