Brennan, 48, of San Jose, was arrested about 8 p.m. Wednesday after police had him under surveillance for a few days, the San Jose Mercury News reported. He was being held on $1 million bail after being booked on two counts of arson, though additional charges were expected.
Police said Brennan was convicted in 2001 of one count each of sexual battery and assault for molesting an underage relative of his girlfriend. He was also convicted for setting 16 fires in the Santa Clara County foothills in 1999.
In the current case, Brennan is accused of setting 12 structures on fire throughout San Jose in five days.
"We're extremely certain we have the individual responsible for all the arsons that occurred in the city," said Eddie Garcia, assistant chief for the San Jose Police Department. "We're confident he acted alone in this."
No motive had been revealed.