Dylan Kurihara was found by Rowdy Metzger, a private citizen helping police search for the boy some 25 hours after he was last seen leaving a wedding in an SUV with his father at the wheel, Pasadena police chief Phillip Sanchez told reporters at a news conference.
Sanchez said Dylan appeared to be fine, but paramedics were examining him.
"He is in good shape and none the less for wear," Sanchez said.
Dylan and his father Joe Kurihara, 23, left the wedding at a Pasadena Masonic lodge at about 9:30 p.m. Saturday night.
About an hour later, police arrested Joe Kurihara on suspicion of public intoxication, police said. The father was alone and on foot and police said he was too drunk to remember he had left the wedding with his child.
The boy's mother reported the pair missing Sunday morning and set off the search.
Some 50 police officers and many private citizens, such as Metzger, combed Pasadena and surrounding areas for about 14 hours until the boy was found.
"I was a little afraid when I walked up to the car," Metzger told CBS News, "because I didn't know what I would find. And I saw there was a car seat. It was very dark. I tapped on the window, and he woke up. I knew he was sleeping. and I checked the door. the door was open. I opened the door. I called out his name. He was a little startled."
Police said they took Kurihara back to the wedding site to jog his memory, but he couldn't remember where he had left the boy and the car.
Joe Kurihara was being held on $10,000 bail Sunday night. Police reached by phone said they did not know whether he had hired an attorney.
"We're looking at all possible charges that would be associated with this," Sanchez said.