The burglary attempt soon ended with the suspect in a chokehold, ABC affiliate KGTV reports.
Fighter Sergio Hernandez Jr. trapped the intruder with a triangle chokehold, a move he's used plenty of time in professional fights.
Depending on how he applies it, the person in the chokehold can lose blood circulation in their head and pass out.
In this case, the suspect didn't pass out, but he was held in place until police arrived.
Hernandez is an award-winning mixed martial arts fighter and says he could have approached the situation with a lot more intensity than he did.
"Deep down in my heart I guess I wanted to break the dude's arm, but I don't get a kick out of hurting people," he said.
Hernandez is also a popular artist at Pop's Tattoos in the City Heights neighborhood of San Diego.
After making his citizen's arrest, he went back to work making art.