This review is focused on the durability aspects of timber structures strengthened with fibre-reinforced polymer (FRP) composites. Although FRP composite enhances the strength and stiffness of the timber, the reliable durability of FRP-wood composite structures is a concerning issue. Indeed, because of the interface degradation between the timber and FRP when exposed to environmental conditions, FRP strengthened timber structures may experience delamination and premature failure. This paper presents an overview of experimental investigations, concentrating on the performance of wood-FRP composite hybrid structures exposed to different environments. Over 100 research studies in this field have been reviewed. Generally, the performance of FRP-reinforced wood members deteriorates when they are subjected to a harsh environment such as moisture, elevated temperature, acidic, and alkali agents. The degradation level depends significantly on the type of environment, the type of adhesive and fibres, as well as conditioning duration. Besides the quantitative degradation values of mechanical characteristics, failure modes together with degradation mechanisms before and after conditioning are discussed. Finally, some recommendations for future studies are outlined.