We examined the influence of forest edge effects on activity budgets, feeding ecology, and stress hormone output in five groups of Verreaux’s sifakas (Propithecus verreauxi) in western Madagascar. Sifakas in the edge habitat travelled more, tended to have smaller home ranges, had lower fruit consumption, higher stress hormone levels, and lower birth rates than sifakas in the forest interior. Hence, Verreaux’s sifakas appear to be sensitive to microhabitat characteristics linked to forest edges.