Walsh was with the Jacksonville Jaguars the previous eight years. He also was an assistant in Seattle and Tampa Bay during his 15-year coaching career in the league.
The Lions also hired assistant wide receivers coach Seth Ryan along with defensive assistants Kelvin Sheppard and Brian Duker.
Detroit is retooling mode under Campbell and first-year general manager Brad Holmes.
When the new league year starts in March, the Lions plan to trade quarterback Matthew Stafford to the Los Angeles Rams for quarterback Jared Goff, two future first-round draft picks and a 2021 third-round pick.