Growing up poor, he would visit a nearby smoke shop on weekends, where the proprietor let him read comics for free.

Upon graduation from Sheridan College in 1990, DeBlois was hired by Sullivan Bluth Studios in Dublin, Ireland.

There, he worked as a layout artist, character designer, and storyboard assistant to Don Bluth on such feature animated films as A Troll in Central Park and Thumbelina.

Following its release in 2002, DeBlois sold several original live action feature film projects to write, direct, and produce, including an Irish ghost story titled The Banshee and Finn Magee,[6][1] a psychological thriller titled The Lighthouse,[7] and a family adventure series titled Sightings,[8] which were optioned at Walt Disney Pictures, Touchstone Pictures, and Universal Studios respectively.

DeBlois' feature-length music documentary film Heima chronicles the homecoming concert of Iceland's Sigur Rós.