The volume of evidence from scientific research and wider observation is greater than ever before, but much is inconsistent and scattered in fragments over increasingly diverse sources, making it hard for decision-makers to find, access and interpret all the relevant information on a particular topic, resolve seemingly contradictory results or simply identify where there is a lack of evidence. Evidence synthesis is the process of searching for and summarising a body of research on a specific topic in order to inform decisions, but is often poorly conducted and susceptible to bias. In response to these problems, more rigorous methodologies have been developed and subsequently made available to the conservation and environmental management community by the Collaboration for Environmental Evidence. We explain when and why these methods are appropriate, and how evidence can be synthesised, shared, used as a public good and benefit wider society. We discuss new developments with potential to address barriers to evidence synthesis and communication and how these practices might be mainstreamed in the process of decision-making in conservation.