Julio Castillo enters his third season as an assistant coach with NNU in the fall of 2023.

A 2015 graduate of Northwest Nazarene, rejoined the NNU men's soccer staff in 2021 after spending two seasons as an assistant at nearby College of Idaho.

Castillo had previously been an assistant with the Nighthawks in the 2017 and 2018 seasons. He starred for NNU as an athlete in 2014 and 2015, winning the GNAC Player of the Year award and being named a Second Team All-American his senior year by the National Soccer Coaches Association of America. He was also the GNAC Newcomer of the Year as a junior and made the NSCAA All-America first team.

Before NNU he played two years at Arizona Western College where he was all-conference twice, all-region twice, and was named to the National Soccer Coaches Association of America All-America first team.

He started his playing career at the Monterrey Academy in Mexico, playing for the Under-15 and Under-17 Mexican National Team. He later played for the Under-20 US National Team. He also played professionally with Savsjo in Sweden.

Castillo played club ball for the PDL Burlingame Dragons in 2015, as well as various appearances for the Under-20 "Rayados de Monterrey" Reserve team, the third-division "Halcones de Tijuana," the first, second and third divisions in "Rayados de Monterrey" Reserve team and the Under-17 in "Rayados de Monterrey" Reserve team.

Castillo scored five goals and had 24 assists in 36 matches at NNU and was a team captain and starter both years.