Following his amateur career, Fieldgate was recruited by CFL legend and first head coach of the BC Lions Annis Stukus, to join the BC Lions for their inaugural, 1954 season. Fieldgate played tight end, defensive end, linebacker, and defensive back for the Lions over his 14-year career, but achieved the most success as a linebacker.
In the 1962 CFL season, Fieldgate was honoured with a "Norm Fieldgate Night" by the BC Lions, the second player to receive such an honour. The 1965 CFL season saw Fieldgate win the Bobby Bourne Memorial Trophy as the Lions' "Most Popular Player." Fieldgate was inducted into the BC Sports Hall of Fame in 1970, and was inducted into the Canadian Football Hall of Fame in 1979. In 2003, Fieldgate was voted a member of the BC Lions All-Time Dream Team, at the linebacker position, as part of the club's 50 year anniversary celebration. In November, 2006, Fieldgate was voted to the Honour Roll of the CFL's top 50 players of the league's modern era by Canadian sports network TSN.
Following his retirement from the BC Lions in 1967, Fieldgate started his own company, and worked for the BC Lions as president in 1989. He remains active with Lions' alumni and charitable events in the greater Vancouver area.