Geary generally plays as a half-back or midfielder and has shown he is a hard-nosed player.
Geary is a product of Eaglehawk Football Club and also played in the TAC Cup for the Bendigo Pioneers with Geelong star Joel Selwood. Despite winning Bendigo's best and fairest in 2006, he was passed over in the national draft and eventually taken by the Saints with pick 58 in the rookie draft. At the end of 2007 he was elevated to the senior list and played 10 games in 2008. He played in eight of St Kilda's wins, earning the Rising Star nomination for his 19-possession game against Essendon.
In 2008 Geary played well throughout St Kilda’s 2008 NAB Cup winning campaign.
In Round 1, 2008, Geary gained 30 possessions and was one of the best-on-ground against the Sydney Swans.
Geary played in 15 of 22 matches in the 2009 season home and away rounds in which St Kilda qualified in first position for the AFL finals series.
Geary played his 100th AFL game in Round 7, 2014 against Hawthorn, but the milestone was to be remembered for all the wrong reasons; not only did the Saints lose by 145 points, Geary also suffered a broken arm that consequently ended his season.
In 2015 he was added to St Kilda's leadership group.