Kirk first broke into the comics field pencilling issue #5 of Malibu Comics' title Dinosaurs for Hire and issue #1 of Captain Canuck vol.2. He then went on to pencil Star Trek: Deep Space Nine comics for Malibu.
In 1995, he began working with Marvel comics, penciling the Barbara Kessel penned Ultragirl miniseries.
In 1997, he began a long association with DC Comics, beginning with a nearly 60 issue run on the Peter David penned Supergirl series.
His current work can be found in the One Year Later story Face to Face, running through Batman/Detective Comics series.
Later in 2006, Kirk signed an exclusive deal with Marvel Comics, his first project being a 5 issue Agents of Atlas miniseries.