First published by Lester and Orpen Dennys in 1981, it chronicles Canada's internment and persecution of its citizens of Japanese descent during the Second World War from the perspective of a young child.

Themes depicted in the novel include memory and forgetting, prejudice and tolerance, identity, and justice versus injustice.

Set in Canada, Obasan centers on the memories and experiences of Naomi Nakane, a 36-year-old schoolteacher living in the rural Canadian town of Cecil, Alberta, when the novel begins.

Her brief stay with Obasan in turn becomes an occasion for Naomi to revisit and reconstruct in memory her painful experiences as a child during and after World War II, with the aid of a box of correspondence and journals sent to her by her Aunt Emily, detailing the years of the measures taken by the Canadian government against the Japanese citizens of Canada and their aftereffects.

Naomi's narration thus interweaves two stories, one of the past and another of the present, mixing experience and recollection, history and memory throughout.