Keown moved to Marvel Comics in 1989, where he first worked on Nth Man: the Ultimate Ninja, before replacing Jeff Purves on The Incredible Hulk.

Keown worked on Hulk with writer Peter David, creating one of the more memorable runs of the book.

David has named Keown one of the three artists whose art has mostly closely matched the visuals he conceived when writing a comic book scripts (the others being George Pérez and Leonard Kirk).

Keown was originally offered "founder" status at Image after Whilce Portacio withdrew to deal with his sister's illness[3] but declined due to having a criminal record making traveling outside of Canada difficult.

He eventually began working for other companies once more, drawing The Darkness for Top Cow and teaming up with Peter David once more with Hulk: The End for Marvel.