Parnell made his first-class debut for Eastern Province in October 2006, at the age of seventeen, against South Western Districts scoring 17 and taking one wicket. In his second first-class match, he recorded figures of four for seven,and, in only his fifth first-class match, he took a hat-trick against Western Province: all three batsman were bowled. He was described as “the most talked about cricketer to hit the first-class scene for some time.”
In 2008 Parnell was awarded the Coca-Cola Khaya Majola U19 Player of the Tournament and the CSA U19 Cricketer of the Year while representing Eastern Province.
At the start of the 2009 season Parnell was signed as an overseas player by Kent on a six-week contract, serving as a replacement for Stuart Clark.On his county debut against Essex he took 4/78 in the first innings and top scored with 69 in the second, his maiden first-class fifty the innings contained 11 boundaries. Despite following on Kent won the match, with Parnell claiming three further wickets. In Kent’s next first-class match, against Glamorgan he bettered his maiden fifty with an innings of 90, again top scoring from number eight.Parnell left Kent to join up with South Africa ahead of the World Twenty20, but after the tournament he returned for a further five weeks. Opening the bowling in Kent’s successful defence of 149 runs against Durham in the Twenty20 Cup quarter-final, Parnell dismissed opening batsmen Phil Mustard for a golden duck from the first delivery of the Dynamos’ run chase and David Warner in the second over of his spell, also for a duck. Though returning to South Africa after his second spell ends, Parnell has been cleared by Cricket South Africa to return to Kent and feature for the Spitfires on finals day of the competition