Eastvale police say the 4-year-old boy slipped under water around 1:40 p.m. at the pool in the 12000 block of Gathering Place.
Police say his father was distracted for a moment, but the boy's older brother acted quickly and pulled him out of the pool. Off-duty paramedics, who were also there, performed CPR.
The boy was revived and transported to Loma Linda University Medical Center. He was expected to make a full recovery.