The costs and benefits of the Reducing Emissions from Deforestation and Forest Degradation (REDD+) projects are often reported in isolation. There is a lack of comprehensive understanding of the types of REDD+ costs and benefits reported in the literature. In this paper, we conducted a review of 60 unique REDD+ costs and benefits studies. We found that no single study covers all categories of costs and benefits in a comparable form. A total of 56 comparable estimates were available for opportunity costs, 21 for transaction and implementation costs, 23 for total costs, and only four for direct monetary benefits. We found that, on average, the total REDD+ cost ($24.87/tCO2e) was 2.23 times higher than the opportunity cost and the opportunity cost was 3.28 times higher than the transaction and implementation costs. Costs estimates among studies vary widely based on estimation approach used and the scale of the studies. We noted that future REDD+ costs and benefits studies should provide estimates of all relevant costs and benefits, and the distribution of these costs and benefits among project stakeholders. These findings have implications in REDD+ project design and implementation.