Career
Adelaide United
Cornthwaite signed for United for the inaugural A-League season and spent the majority of his first two seasons starting on the bench. As of half time of Adelaide United"s away game against J League 5 time champions Kashima Antlers in the quarter finals of the 2008 AFC Champions League, Robert scored an accidental own goal to put Kashima level with Adelaide 1–1 after a spectacular goal from Adelaide captain Travis Dodd which came after a cross from vice-captain Lucas Pantelis in the 38th minute. The match being the first leg of the 2 teams Quarter finals match dated on Wednesday 17 September in Japan.
Cornthwaite signed a new three-year contract with Adelaide United in October 2009.
Jeonnam Dragons
On 8 March 2011, Cornthwaite announced that he had signed for Jeonnam Dragons in the Korean K-League on a 2-year contract. Selangor
Robert joined the Malaysian Super League outfit in early 2015 and have scored a few goals for the club
He has a wage of RM 80,000 per month. He is also selected to play for Malaysian XI in a friendly match against Tottenham Hotspurs in July 2015.
In January 2016 his contract with Selangor FA was continued after Selangor fans forced the Football Association of Selangor to continue his contract by using the social media.
Cornthwaite made his first senior international debut for the Socceroos on 4 March 2009 in an AFC Asian Cup qualifying match versus Kuwait. He scored his first international goal in against South of Korea in a 2012 friendly. International goals.