After going undrafted in the 2011 NFL Draft, Bighill signed as a free agent with the BC Lions of the Canadian Football League (CFL) on May 31, 2011. Bighill had an impressive rookie season, playing an increased role as the season progressed. He played in 12 games, including the final seven regular season games, and the West Final and Grey Cup games. He led the club, and was ranked fourth overall in the CFL, with 22 special team tackles.
Bighill began the 2012 CFL season by replacing Solomon Elimimian at middle linebacker for the Lions, after Elimimian was signed by the Minnesota Vikings. After assuming the starting linebacker role Bighill went on to amass 104 tackles (2nd most in the CFL) and 4 interceptions. Elimimian returned to the Lions midway through the season, but Bighill retained all of the playing time. He was named both a CFL West All-Star and a CFL All-Star for the 2012 season.
Bighill and Elimimian both returned to the Lions linebacker core for the 2013 CFL season. Bighill suffered a sprained ankle and missed Week 3 and 4. He played in the 16 other regular season games, and the Lions lone playoff game. Bighill put together a strong 2013 season, accumulating 92 tackles, 12 special teams tackles, 9 sacks, 1 interception and 3 fumble recoveries (one of which he returned for a touchdown; his first of his career). In 2014 Bighill played in all but one of the 18 regular season games as well as one playoff game. He totalled 77 tackles, 12 special teams tackles, 6 sacks, 1 interception, and 1 fumble recovery. Following the season, Bighill's linebacker teammate, Solomon Elimimian, was named the leagues MOP, and both of them signed 3-year contract extensions on the same day.
In Bighill's fifth season with the Lions he played in all but one game of the regular season, contributing a league leading 117 tackles. Following the season Bighill was named the CFL's Top Defensive Player. Bighill continued his dominant play in the 2016 season finishing 3rd in the league in tackles and earning his fourth CFL All-Star award in the past five seasons. On December 9, 2016, the BC Lions granted Bighill a release as per the agreements in his contract which allows him to pursue an NFL contract up until January 27, 2017. If he is unable to sign an NFL contract by that date he will be back under contract with the BC Lions through the 2018 CFL season. Through six CFL seasons Bighill amassed 489 defensive tackles, 69 special teams tackles, 33 sacks, 8 interceptions, 8 forced fumbles and 1 defensive touchdown.
Bighill had a workout with the New Orleans Saints on December 13, 2016.
Bighill signed a future/reserve contract with the New Orleans Saints on January 4, 2017. Bighill drew strongly positive attention for his performance during the Saints training camp and preseason. He was waived on September 2, 2017, and was signed to the Saints' practice squad the next day. He was promoted to the active roster on September 11, 2017. He was released the following day, and re-signed to the practice squad on September 14, 2017.
Bighill was born with a bilateral cleft lip and palate. He is on the board of Toronto-based charity Making Faces, a charity dedicated to helping people cope with facial differences.