Leiren-Young's documentary, "The Hundred-Year-Old Whale" (2017), which he wrote and directed, won the 2017 Writers Guild of Canada award for "best documentary." The movie explores the life of Granny (orca) and the history of our relationship with the Southern resident killer whales. Leiren-Young's first feature film, The Green Chain (2007), which he wrote, directed and produced, explores the issues facing dying logging communities in British Columbia. The movie won the El Prat de Llobregat Award at the 15th Annual Festival Internacional de Cinema de Medi Ambient (FICMA 2008) in Barcelona."Mark Leiren-Young honoured at Barcelona film festival". The Georgia Straight, June 10, 2008. Leiren-Young also has extensive television writing credits, with over 100 hours of produced work.
