Walker began his coaching career as an undergraduate assistant coach for the
UCLA Bruins in 1984. He spent 11 years at UCLA where the Bruins won six
Women's College World Series championships in
1984,
1985,
1988,
1989,
1990 and
1992. Prior to the 1995 season, Walker was named head coach for the
Oregon State Beavers softball team. In 1999, he led the Beavers to a 47–25 record, setting a program-record for the most wins, and advanced to
NCAA Tournament for the first time in program history. Following the season he was named
Pac-10 Coach of the Year and Speedline Pacific Region Co-Coaching Staff of the Year. In 2005 he led the Beavers to a 43–16 record, and their first-ever conference championship in program history and an automatic berth to the NCAA Tournament. The Pac-10 championship was the first regular-season title for any women's sports program in Oregon State history. Following the season he was named Pac-10 Coach of the Year. Walker served as the head coach at Oregon State for eighteen years, where he posted a 594–490–3 record, and eight seasons with at least 40 wins. He is the all-time winningest softball coach in program history and the fifth-winningest in Oregon State history regardless of sport. On August 7, 2012, Walker resigned as head coach of the Beavers to return to UCLA as an assistant coach. On August 12, 2022, Walker was promoted to associate head coach for the Bruins. He transitioned to director of softball administration in 2025. On November 18, 2019, Walker was named head coach and assistant general manager for the
California Commotion of
National Pro Fastpitch. The team never played a game as the
2020 and
2021 seasons were cancelled due to the
COVID-19 pandemic. On August 1, 2021, the NPF announced that due to a lack of revenue after cancelling the previous two seasons, it would be suspending operations. ==Later years==