Courtney began his motorsport career in karting in 1987 and was active until 1998 in this sport. In 1999 he moved to Formula racing and was fifth in the British Formula Ford 2000, he remained in this championship and won with six wins from 14 races the championship ahead of Mark Taylor. In 2001 he moved to the British Formula 3 Championship, where he competed as team-mate André Lotterer Junior for the Jaguar team. The Australian won the season opener and was later in the season nine times on the podium. The season he finished as the best pilot of his team in fourth place in the championship.
In 2002, Courtney within the British Formula 3 Championship at Carlin Motorsport. In addition, he was a test driver of the Jaguar Formula 1 team. Courtney initially won four races in the British Formula 3 Championship and led the championship. In Formula 1 testing during the season in Monza he had a serious accident. At a speed of 330 km / h the rear suspension of the Jaguar broke. Courtney hit 306 km / h in the wall and was thrown back on the track. The impact of delay 67g was measured. The brain of the racer was crushed in the accident and after the accident he had deficits on its right half of the body. Courtney suffered a further year from the consequences of the accident and had in this period a severe migraine. He also took part only at another Formula 1 test. In the British Formula 3 Championship Courtney let out a race weekend and then returned. Although he managed another victory, for winning the league title but it was not enough. The rider was eventually runner-up behind Robbie Kerr.
2003 Courtney left Europe and moved to the Japanese Formula 3 Championship. He won 13 of 20 races and secured the championship title against Ronnie Quintarelli. He also made his debut this season in the Formula Nippon. He competed in four races and finished the season 13th overall. In 2004 he returned to the Formula racing back and moved to the GT racing. He remained two years in the Japanese GT Championship Super GT and finished both seasons in seventh place overall. Overall, he stood on the podium four times.
After Courtney had already in 2005 in a Holden Commodore, participated in two races of the V8 Supercar, an Australian Touring Car Championship and the season had ended on the 47th place overall in 2005, he joined in 2006 to complete in this series. He changed the brand and launched for Stone Brothers Racing in a Ford Falcon. The Australian finished four races and finished on the podium at the end of the season in eleventh place overall. In 2007, he improved with seven podium finishes in ninth place overall. In 2006 he succeeded in the Ford Falcon, the first win in the V8 Supercar. In the championship, he improved to sixth place overall.
In 2009 he moved to Dick Johnson Racing, which also employing an optical Ford Falcon. Courtney won two races and finished the season in seventh place. In 2010 he fought a duel with Jamie Whincup for the title of the V8 Supercars. While Whincup won with nine wins more races than Courtney, who won five races for themselves, but the championship went to Courtney, who decided the title fight with 3055 to 2990 points for themselves.
Courtney is married and the father of two children ( one daughter, one son).