Grew up playing Arroyo Seco Golf Course, a par-3 course in South Pasadena, California.

Grew up skateboarding and dreamt of becoming the next great skateboarder, with his icons being Tony Hawk, Andrew Reynolds, and Erik Ellington. Around the time he was five years old, a skating accident led to Spaun to rethink his dream. Received an autographed skateboard from Tony Hawk in the weeks following his victory at the 2025 U.S. Open.

Attended San Dimas High School in San Dimas, California, the same high school that Bill and Ted attended in the movie "Bill & Ted's Excellent Adventure."

While at San Diego State University, the men's golf team annually worked at the Farmers Insurance Open at Torrey Pines, with team members cleaning shoes of the TOUR pros in the locker room to raise money for the program. Spaun recalled, "It was good memories to go from cleaning shoes to now playing in the tournament."

According to J.J., his mother's side of the family is predominantly half Filipino and half Mexican.

Plays the guitar and has an interest in music. Can play Led Zeppelin's "Stairway to Heaven" on the guitar. Previously used custom Led Zeppelin headcovers early in his professional career.

Previously a season-pass holder for Disneyland. His trips to Magic Kingdom typically began with a ride on the Pirates of the Caribbean attraction.

Played four seasons at San Diego State University (2008-12), where he was credited with five collegiate wins, earned two All-America honors, and was named the 2012 Mountain West Conference Golfer of the Year.