Griffith played major junior hockey with the London Knights of the Ontario Hockey League. With the team, he would win two consecutive OHL Championships and thus participate in two Memorial Cup tournaments. Griffith was rewarded for his outstanding play during the 2012–13 OHL season by being named to the OHL's First All-Star Team, one year after he was named to the Second All-Star team. Griffith's first career NHL goal was scored on October 21, 2014 against San Jose Sharks's goaltender Antti Niemi. Griffith dominated at the AHL level ever since debuting in 2013–14 season. Havng recorded at nearly or over a point-a-game in all seasons since, he experienced a phenomenal 2015–16 campaign which saw him finish second in league scoring and was named to the AHL First All-Star team. In total, he recorded 77 points in 57 games played. In reward for this, he was signed to a one-year, two-way contract extension on May 24, 2016. On the eve of the 2016–17 season, Griffith was claimed off of waivers by the Toronto Maple Leafs on October 11, 2016, after he was placed on waivers the previous day. Leafs assistant general managerMark Hunter and his team was responsible for the pick-up; Hunter have previously worked with Griffith within the London Knights organization. Griffith appeared in 3 games with the Maple Leafs, however largely served as a healthy scratch over the first month of the season. On November 12, 2016, Griffith's brief tenure with the Maple Leafs ended after he was again claimed off waivers, by the Florida Panthers. Griffith was inserted in the Panthers scoring line, however after a positive start, found a reduced role with 5 assists in 21 games. On January 19, 2017, Griffith was again placed on waivers and was re-claimed by the Maple Leafs for a second time. With the Leafs the only team vying for his services, Griffith was directly assigned to AHL affiliate, the Toronto Marlies on January 20, 2017. He would remain with the Marlies for the rest of the season, playing at a pace of over a point-per-game. On July 1, 2017, Griffith signed a one-year, one-way $650,000 contract as a free agent with the Buffalo Sabres. Griffith made the Sabres opening night roster for the 2017–18 season, however was unable to take his opportunity, producing just 2 goals in 21 games in a depth role. He was assigned to AHL affiliate, the Rochester Americans, throughout the season, posting 41 points in 46 games. As a free agent from the Sabres, Griffith joined the Winnipeg Jets on a one-year, two-way $650,000 contract on July 1, 2018.
