Life cycle assessment (LCA) has been widely used to determine the environmental impact of mass timber construction (MTC) as a substitute for conventional construction. This article presents a systematic review of MTC from a life cycle assessment perspective. The goal and scope definition, life cycle inventory analysis, impact assessment and interpretation are examined and analyzed in 62 peer-reviewed articles. The results show the variety in scope, lifespan, system boundary, data sources and indicators. Studies on MTC have been conducted at the building material, component, structure, and entire building levels, as well as at the urban level. The majority of studies compare the LCA of reinforced concrete (RC) and cross laminated timber (CLT) buildings. The global warming potential (GWP) and life cycle energy are the most frequently evaluated category indicators among the articles. It is found that the average embodied energy of mass timber buildings is 23.00% higher than that of RC alternatives, while the average embodied greenhouse gas (GHG) emissions of RC buildings are 42.68% higher than that of mass timber alternatives. There is a clear general trend that mass timber buildings generally have lower GWP and life cycle primary energy (LCPE) than RC and steel buildings. Eventually, sensitivity analysis, carbon storage and outlook of the mass timber are also reviewed and discussed in the literature.