In 1999–2000 Gillies made his professional debut with the Mississippi Sea Wolves in the East Coast Hockey League.

With limited offensive ability Gillies plied his trade between the ECHL and American Hockey League (AHL) for five years before signing an NHL contract with the New York Rangers on July 20, 2004.

[4] On March 14, 2010, Gillies scored his first NHL point, when he assisted on a Tim Jackman goal in a 4-2 victory over the Toronto Maple Leafs.

During the third period of the game, Gillies elbowed Penguins' forward Eric Tangradi in the face, punched him several times while he was down on the ice, and proceeded to taunt him from the dressing room hallway.

[10] On June 19, 2012, Gillies opted to forgo North American free agency and signed a one-year contract to play with Vityaz Chekhov of the Russian Kontinental Hockey League.

[12] On October 10, 2014, after signing with the Adirondack Flames, Gillies slammed the face of Rochester Americans' William Carrier into the ice, receiving a 12-game suspension.