John Henderson joined the PDC professional tour after successfully coming through the qualifying school. His solid performances saw him reach the top 50 in the world rankings in just twelve months.

Henderson had enjoyed some success in his early career, including hitting a record breaking 13 180s in a second round match at the 2005 BDO World Championship. He made it to the quarter-finals of the British Open in the same year.

In 2007, Highlander beat Ted Hankey and Tony O’Shea on his way to the final of that competition, but he was denied victory by compatriot Gary Anderson.

Over the next two years, Henderson enjoyed regular success, winning five Open titles. His first came at the 2008 British Open, where he exacted revenge on Anderson for the defeat the previous year. In 2009, he triumphed at the Scottish National Championship, Belgian Open, Didam Open and German Open. The Scotsman climbed to seventh in the World Darts Federation rankings on the back of that success.

Henderson joined the PDC in January 2011 and immediately made an impact, hitting a nine-dart finish at the Derby Championships.

In his first year on the PDC circuit, Highlander qualified for five major tournaments. His best performance was reaching the quarter-finals of the World Grand Prix.

Henderson made his debut at the 2012 PDC World Championships, but was unable to overcome three-time world champion John Part.

In the 2014 World Championship, Henderson knocked out number nine seed Dave Chisnall in the first round.

In April 2015, Henderson enjoyed his best ever run in a PDC tournament when he reached the final of the German Darts Masters in Munich. The Scottish ace defeated Brendan Dolan with a 107 average and double World Champion Adrian Lewis before losing out to world number one Michael van Gerwen 6-5 in the final.