Many global environmental threats are driven by human behavior and require behavioral solutions. Researchers in the environmental field have recently begun seeing the behavioral sciences as core to changing behavior for conservation; yet leveraging human emotions remains an underused tool for behavior change compared to others like social norms. Humans experience a range of emotions that each cause distinct patterns of behavior depending on unique contexts; this presents an opportunity to leverage emotions to support behavior change goals. The existing literature offers minimal guidance about which specific emotions to use in which contexts and how those emotions might lead to certain behaviors. In the environmental field specifically, there have been mixed results on using emotions, resulting from an incomplete understanding of the causal relationship between particular emotions, contexts, and environmental behaviors. We propose that adopting a functionalist approach, which describes emotions as functional states designed to produce particular outcomes in specific contexts, will help to unlock emotions as a tool for conservation. To demonstrate this approach, we identify fear, joy, hope, anger, pride, interest, and the prospect of shame as particularly relevant for environmental behavior change. Based on an understanding of each emotion’s function, we developed an emotion-behavior pathway that describes the expected outcome of using an emotion in a particular context. Applying these emotional-behavior pathways can allow both researchers and practitioners to advance the science of shifting environmental behavior through emotion.