On 13 November 2006, Grella was selected as captain for an international friendly in London against Ghana, making him the 51st player to captain the Australia football team. On 21 July 2007 in Hanoi, Vietnam, Grella was sent off in the 76th minute of Australia's 2007 Asian Cup quarter-final against Japan. Leaping for a header, Grella's forearm connected with Naohiro Takahara's head, who had come from behind Grella, sending the latter to the ground. The game was 1–1 at the time and remained that way until the end of extra time, with Japan eliminating Australia from the tournament in a penalty shoot-out. He has currently amassed 46 caps for Australia since making his debut back in February 2003.