Begley played his very first game of Australian rules immediately after moving from Ireland to Australia in 2006. In just his third game weeks later, he lined up in a NAB Cupquarter final. In that game he picked up a total of six possessions and one mark whilst playing on Melbourne speedster Aaron Davey. He was later elevated to the senior list during the regular season when the Lions suffered a string of injuries. In his senior debut against the West Coast Eagles he gathered seven possessions, seven marks and two hitouts, lining up on Brownlow Medallist Chris Judd. At the end of the season he was retained by the club as a rookie listed player. Following his good form through the 2007 NAB Cup, Begley was once again elevated onto the Brisbane Lions' senior playing list and was soon after named on the interchange bench in the Lions' first game for the season. He was soon playing regularly for the Lions. Begley was named the club's Rookie of the Year in 2007. His rise after such a short time playing the sport was described as 'remarkable'. However, Brisbane opted not to offer him a new contract for the 2009 season following an injury ravaged 2008 which restricted him to only eight appearances. Begley represented Ireland in the senior 2008 International Rules Series with rumours of his delisting circulating; many commentators claimed that he was playing for his career. During this time he said that if his AFL career was over he would return to play Gaelic football with Laois. He appeared in both matches in the series, which Ireland won.
In the hope that he would be redrafted, Begley trained with Collingwood prior to the 2008 AFL Draft. He was eventually selected by St Kilda at pick 83. Begley played in only one of the 22 matches of the 2009 AFL seasonhome and away rounds in which St Kilda qualified in first position for the finals, winning the club’s third minor premiership. After the 2009 AFL season, Begley retired from the AFL, announcing his desire to return to Ireland.
Return to Ireland and senior Gaelic football
Begley is currently playing for Dublin side Parnells and has returned to inter-county football with his native Laois. Begley has represented his country in the International Rules Series on no less than 12 occasions; in 2006, 2008, 2010, 2011, 2013, 2014 and 2015. He is one of only six players to have played 12 or more games in the series and he is one of only two players to have won nine tests. He has scored a total of 15 points for Ireland and is the second-highest scoring Laois player in the series.