Kirk first broke into the comics field pencilling issue #5 of the 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, penciling the Ultragirl miniseries.

In 1997, he began a long association with DC Comics, beginning with a nearly 60 issue run on the Peter David written Supergirl series. Following that, he penciled the Dan Jolley written Bloodhound, which was canceled in under the year.

He penciled the Fred Van Lente written Scorpion story in the Marvel anthology title Amazing Fantasy. Following that, he illustrated the acclaimed[citation needed] humorous miniseries, Freshmen, written by Seth Green and Hugh Sterbakov, for Top Cow.

He returned for a year to work at DC, filling in on Aquaman and doing the layouts in Detective Comics’ “One Year Later” storyline Face the Face that ran through both Batman and Detective Comics.

Later in 2006, Kirk signed an exclusive deal with Marvel Comics,[citation needed] his first project being a five issue Jeff Parker written Agents of Atlas miniseries, which included Wakandan-born S.H.I.E.L.D. agent, Derek Thanaka from the Scorpion story he penciled in Amazing Fantasy. Marvel has proceeded to assign him to pencil Marvel Adventures: The Avengers (from issue #13 onwards), Spiderman Family, and a fill-in for the World War Hulk storyline in The Incredible Hulk #108.

Kirk’s most recent projects including providing the art for Captain Britain and MI: 13, written by Paul Cornell