Walsh was a third-string goalie for Bowling Green State University. As a sophomore, he decided to concentrate on coaching as a volunteer assistant for the BGSU hockey team. He was graduated from Bowling Green with a bachelor's degree in education. He later earned a master's degree in the same field of study.
After completing his undergraduate studies, Walsh was hired as a full-time assistant coach at BGSU by Ron Mason. Walsh followed Mason to Michigan State in 1979 where they inherited a program that had only won 36 games in its previous three seasons. After only five years, Mason and Walsh had guided MSU to three-straight NCAA Tournament appearances, back-to-back 30-win seasons and the 1984 Frozen Four--the school's first Frozen Four appearance in 17 years.
In 1984 Walsh took over a Maine program that had gone 27-65 in the three seasons prior. He built the program into a national power, winning national championships in 1993 and 1999. The 1992-93 Maine team finished the season with an astonishing 42-1-2 record. Maine was also national finalists in 1995. He coached Hobey Baker Award winners Scott Pellerin (1992) and Paul Kariya (1993).
Walsh was suspended from coaching for one year starting mid-season in 1995-96 after a series of NCAA investigations. He returned during the 1996-97 season and quickly built Maine back into a national contender.
Walsh was diagnosed with a rare form of cancer known as renal cell carcinoma in June 2000. At the time of his death he was only 46 years old. Walsh had a career record of 399-215-44.