The importance of scientific evidence in ecology and conservation has gained increasing recognition over the past 15 years. A systematic compilation of evidence and its use in practice were first conceptualised in medicine in the 1970s, and since evidence-based medicine has revolutionised the effectiveness of health care interventions. During the same time period, ecology and conservation science also rapidly accumulated scientific knowledge that could provide invaluable insights for understanding and restoring life on this planet. But are we using this accumulated knowledge effectively? To answer this question, the concept of evidence-based conservation was established in the early 2000s, and increasingly, evidence synthesis has been adopted as a formal approach in ecology and conservation. Today the systematic compilation of evidence plays a vital role in deriving unbiased scientific conclusions and informing policies and practices. This symposium brings together world-leading experts of evidence-based conservation and evidence syntheses, to understand, discuss, and facilitate the use of evidence in ecology and conservation in Japan. Why is using evidence important? How should we compile evidence? How can evidence make a real difference in conservation? We hope that after attending this symposium, you will leave the (virtual!) room equipped with answers to these fundamental questions.