He has produced albums for bands such as Dropkick Murphys, Agnostic Front, the Business, Swingin' Utters, Marky Ramone and the Intruders, Anti-Heros, Pressure Point, and the Forgotten, among others.

[3] Minna Dapello was a Danish immigrant who was the only member of her family to survive the Nazi occupation of Denmark, but witnessed their murder.

They divorced, and he married San Francisco yoga instructor Stephanie Snyder, with whom he had two children, both boys.

On the 75th episode of That One Time on Tour podcast that aired on October 15, 2019, Frederiksen mentioned that he "always liked the idea of a big family," and that he "plans to have more kids at some point in [his] life" and would be open to adoption.

[6] Frederiksen's brother was Robert "Rob" Dapello, a writer for Zero Magazine and a fellow musician, who died in February 2001 from a fatal brain aneurysm.

In January 2014, Lars and the Old Firm Casuals wrote the new team anthem/theme song for the San Jose Earthquakes, titled "Never Say Die".

[12] Frederiksen was involved with San Francisco's Project Homeless Connect, partnering with Tony Hawk to donate skateboards to teenagers in the family shelter.