The former Twilight actor, 28, wed Sheila Hafsadi on Sunday in Los Angeles, his rep confirms to PEOPLE.
"It was a small wedding," a source says. "There were about 150 [guests]."
"We are both spontaneous people. I wouldn't say we are bohemian, but we are both artistic," Rathbone told PEOPLE of meeting Hafsadi in Fort Lauderdale, Fla. in 2011. He had been playing a show with his former band, 100 Monkeys, when he saw her working at the venue next door.
"It was one of those things. I always said I believed in love at first sight, but I never really had that feeling before."
The couple have since become parents to a son, Monroe Jackson Rathbone VI, now 15 months old. Soon after his birth, Rathbone told PEOPLE the pair planned to wed eventually – just not quite yet.
"Honestly, at the end of the day, you don't need a piece of paper to say you are in love," he said at the time. "We are dedicated completely to one another."
And now they've made it official.
Reporting by RAHA LEWIS