Ian left a career in graphic design to work professionally in comics in 1994, when he was hired on the spot at a London comic convention by Marvel’s then editor-in-chief, Bob Harras. Churchill debuted on Marvel’s X-Men titles and, along with Jeph Loeb, took Cable to new heights. Churchill went on to illustrate Avengers, The Uncanny X-Men, Superman, Superman/Batman, Supergirl, Teen Titans, Hulk, Elephantmen and Churchill’s own supernatural group of heroes – The Coven. In December 2010, the first issue of his new creator-owned title, Marineman, launched to critical acclaim, and received an Eisner nomination for Best New Series 2010.

Churchill was part of the second wave of DC's New 52 initiative, penciling The Ravagers and is currently working on a project for Image with Jonathan Ross, called The Revenger. He is also working on volume two of his creator-owned series, Marineman