Police responded to Neil Cooper's home in the 2400 block of Redwood Drive at 2:19 a.m. after receiving a report of a disturbance.
While they were inside the residence, officers found what appeared to be two pipe bombs and other materials used to make explosive devices.
They also found vials of liquid that were cautiously packaged and articles of police attire, police said.
Police evacuated a neighboring home and called the Walnut Creek Bomb Squad to render the pipe bombs safe. Bomb squad personnel determined that the pipe bombs had not been completed and were incapable of detonation.
The Contra Costa County Hazardous Materials unit responded to the residence as well and took the vials of liquid for further testing.
Cooper was arrested on suspicion of making a destructive device without a permit, cruelty to children, violating his probation, possession of fireworks without a permit, possession of a police baton and possession of an illegal magazine for a rifle, police said.