For the next two years Alan Cumyn ran a group home in Toronto for the national youth volunteer organization Katimavik. In 1986 he married and spent the next year in the coal-mining, train station town of Xuzhou, China, teaching English. The year abroad launched a career in various posts in international development, and was the inspiration for both Cumyn's first novel, Waiting for Li Ming, published by Goose Lane Editions in 1993, and for his popular guide to work and study abroad, What in the World is Going On?, first published in 1988 by the Canadian Bureau for International Education (CBIE).

From 1991 to 1999 Cumyn worked for the Immigration and Refugee Board (IRB) of Canada, researching and writing papers on human rights conditions in various countries.

On leave, Cumyn spent the first half of 1994 teaching in Salatiga, Indonesia. His second novel, Between Families and the Sky, was published in 1995, and explores themes of love, family connections and the coming of age. Man of Bone, a harrowing tale of kidnapping and survival inspired by Cumyn's human rights reporting, was published in the spring of 1998. It won the Ottawa-Carleton Book Award a year later, and was short-listed for the Trillium Award.

Burridge Unbound was published in 2000 by McClelland & Stewart. The story continues from Man of Bone, but leaps ahead two years and features a vastly changed central character, torture survivor Bill Burridge, who builds a human rights organization but continues to struggle with inner demons. Burridge Unbound was a finalist for the Giller Prize in 2000 and won the Ottawa Book Award in 2001.

In 2001 Cumyn published Losing It, a darkly funny novel about the eccentric sub-surfaces of contemporary life. A middle-aged English professor, whose wife is coping with a mentally failing mother and a highly-demanding two-year-old, seeks refuge in a bizarre affair with a beautiful, mad poet, in a week that threatens every aspect of his life. Losing It was shortlisted for the Ottawa Book Award.

In 2002, Cumyn published his first novel for children, The Secret Life of Owen Skye, about three brothers whose adventures always seem to spin out of control in unusual ways. The novel was published by Groundwood Books. It won the Mr. Christie's Book Award and the Hackmatack Children's Choice Award, and was shortlisted for the Governor General's Award, the Ruth Schwartz Award, the Rocky Mountain Book Award and the Pacific Northwest Libraries Association Young Reader's Choice Award.

After Sylvia, the sequel to The Secret Life of Owen Skye, was published in 2004. It was nominated for four national awards, including the prestigious TD Children's Literature award and the Canadian Library Association's Book of the Year for Children. In 2005 Cumyn adapted After Sylvia for the stage. The play was produced beautifully by the Ottawa School of Speech and Drama and performed at the University of Ottawa under the direction of Janet Irwin.

Dear Sylvia, the long-awaited third and final novel in the Owen Skye series for children, was published in 2008. It consists entirely of Owen's hilarious and often moving letters to his true love Sylvia Tull, who has moved away to far-off Elgin. Dear Sylvia won the 2009 Silver Birch Express Award and was short-listed for the Canadian Library Association's Book of the Year for Children. Filmmaker Jasmine Murray-Bergquist's tribute to Dear Sylvia can be found on Youtube. 

In 2003 Cumyn published The Sojourn, a novel about Ramsay Crome, a young Canadian private in the Great War who gets an unexpected leave to London. It was awarded the Words Worthy Book Award for best Canadian novel in 2003, was shortlisted for the Ottawa Book Award, and was named among the top Canadian novels of 2003 by The Globe and Mail, The Vancouver Sun, Maclean's and Quill & Quire.

2006 brought The Famished Lover, a sequel to The Sojourn. The novel finds Ramsay Crome trying to support a family as an artist in Montreal in the Great Depression while also struggling to come to grips with his past as a prisoner of war in the Kaiser's Germany. At its heart the novel is about the beautiful, corrosive, ambiguous nature of longing. Taken with The Sojourn, the pair of novels examines in both the short and long term the nature of what we are asking of a person when we send them to war. The Famished Lover has been long-listed for the International IMPAC Dublin Literary Award and the Giller Prize.

Tilt, Alan Cumyn's most recent novel, pitches readers into the wild and often comic romantic obsessions of Stan Dart, a high school basketball player digging in his heels, against high odds, to try to deny the hormonal onslaught of adolescence. The book has been selected by the Junior Library Guild as one of the best young adult novels of 2011.