This article explores the application of ideas from historical institutionalism about path dependence to the study of environmental policy in Madagascar. It first reviews the central components of the historical institutionalism explanation, including the concepts of critical juncture, institutional change and institutional reproduction. This explanation is then applied to an analysis of the “diverging” trajectories of environmental policy in Madagascar during the 20th and 21th centuries. We argue that several historical and institutional events, at the national and international levels, have been critical junctures after which Malagasy environmental policy has shifted to different paths. Copyright © 2012 John Wiley & Sons, Ltd and ERP Environment.