Seagar lives in the small town of Oxford in North Canterbury, with her husband Ross. She initially trained as a nurse, and attended the Cordon Bleu cookery school in London while working at the Royal Free Hospital. Back in New Zealand, Seagar opened Harley's Restaurant in Auckland with fellow nurse Helen Brabazon. Seagar ran "Seagars at Oxford" cooking school, café and kitchenware store for about ten years, but it closed in 2015 after tourism decreased following the Canterbury earthquakes. Seagar was the first food writer for "North &amp; South", has written for "New Zealand Woman's Weekly" and "Cuisine" magazine, and writes a regular column for the "Australian Women's Weekly".