Serrano would become the pitching coach and recruiting coordinator for former Titan head coach Horton and the Titans for the 1997 through 2004 seasons. During Serrano's 8-year tenure at Fullerton, the Titans went 356–154–1 (.698) and were in the NCAA Tournament every season. They won six Big West Conference championships, four NCAA Regionals and four NCAA Super Regionals to earn four trips to Omaha. In 2004, he was named the ABCA/Baseball America Assistant Coach of the Year.