The fire was reported around 10:40 p.m. at a toddler play structure near the south side of the park's playground, according to police.
Fire crews were able to extinguish the blaze but were unable to salvage the play structure.
Several days after the fire, police received a tip that it may have been set intentionally.
Following up on that lead, detectives were able to locate the two teenage suspects and arrested them Thursday evening.
Both suspects were taken to juvenile hall in Martinez, where they remained as of this morning, according to police.
Anyone with information about this case is encouraged to call Antioch police Detective Matt Koch at (925) 779-6895. Those wishing to remain anonymous can text a tip to 274637 (CRIMES) using key word "Antioch".