Over 400 million hectares of tropical forests are managed for timber production, comprising more than half of the remaining global permanent tropical forest estate. A growing proportion of tropical production forests are managed under Sustainable Forest Management (SFM) principles. The objective of SFM is to achieve multiple benefits, including forest protection, biodiversity conservation and income enhancement. However, the outcomes resulting from the implementation of SFM in tropical forest ecosystems have seldom been examined rigorously. In this paper, we present a methodological approach to assess broad-scale impacts of SFM policy in tropical forest ecosystems. As a case study, we investigated deforestation and timber production in logging concessions in the Republic of Congo after the implementation of its SFM-based forestry law in 2000. Compliance with the forestry law was incomplete, allowing a unique opportunity to compare deforestation and legal timber production outcomes in concessions that implemented SFM-based policy compared to those that did not. Quasi-experimental matching analysis indicated that deforestation in matched parcels in compliant concessions was up to 2-times higher than matched parcels in non-compliant concessions, equivalent to 67km2 of forest loss for the period 2005–2010. Annual deforestation data demonstrated that deforestation was stable or increased in all six concessions following the respective date of compliance in each concession. Legal timber production increased (by 5%, from 0.18 to 0.19 CBM/ha/yr) and became more stable, in compliant compared to non-compliant concessions. Our results suggest that the presence of SFM in a concession does not immediately lead to less deforestation. Rather, SFM policy may be associated with higher deforestation, because SFM is also associated with higher legal timber production, foreign capital, and international timber demand. Our findings measure short-term associations between SFM and deforestation in the Congo, and underscore the need for empirical evaluation of long-term impacts of SFM in tropical forest ecosystems worldwide.