Charnley made numerous appearances for the Under 20s in 2010 before joining Blackpool Panthers on dual registration and then Hull Kingston Rovers on loan.

Injuries meant he was given the chance to play first team rugby by Hull KR coach Justin Morgan, making his Super League debut.

Charnley showed great promise on his debut for Hull KR against Leeds Rhinos and picked up the club man of the match award.

Charnley then went onto an even better 2013 season helping Wigan to the double (Challenge Cup winners and Super League champions) scoring a record-breaking 43 tries ranking him first.

[13][14][15][16][17] Although the game ended in a 36–14 defeat for Wigan, Charnley scored two tries in the 2014 World Club Challenge against NRL champions the Sydney Roosters.

Charnley signed off in style as he scored the winning try in the 2016 Super League Grand Final against Warrington, chasing and touching down a beautifully weighted kick from Dan Sarginson at Old Trafford.

[21] On 30 March 2016, Charnley made the cross-code switch to rugby union with Manchester-based Sale Sharks, who compete in the Aviva Premiership, for the 2016–17 season.

[27] In round 3 of the 2023 Super League season, Charnley scored two tries including the winner as Leigh earned their first win back in the top flight defeating Hull Kingston Rovers 30-25.

[30] Charnley played 26 games for Leigh in the 2023 Super League season and scored 27 tries as the club finished fifth on the table and qualified for the playoffs.

[36] He represented England in the 2013 Rugby League World Cup, scoring a try against Australia in the tournament's opening fixture,[37] and a brace against France in the quarter-final.