Oppel was born in Port Alberni, and spent his childhood in Victoria, British Columbia and Halifax, Nova Scotia.

He attended at the same time as actors Andrew Sabiston and Leslie Hope, fellow writers John Burns and Bert Archer, and just before the NBA's Steve Nash and Flickr founder Stewart Butterfield.

Oppel forwarded the newly completed manuscript to a family friend who knew Roald Dahl, who in turn recommended it to his agent.

Oppel went on to receive his Bachelor of Arts degree in cinema studies and English at Trinity College in the University of Toronto, writing The Live-Forever Machine (1992) during his final year.

Oppel moved to England and wrote a number of books during that period, gleaning several ideas while working at typing students' papers.