A growing body of empirical research suggests that brief contact with natural environments improves emotional wellbeing. The current study synthesizes this body of research using meta-analytic techniques and assesses the mean effect size of exposure to natural environments on both positive and negative affect. Thirty-two studies with a total of 2356 participants were included. Across these studies, exposure to natural environments was associated with a moderate increase in positive affect and a smaller, yet consistent, decrease in negative affect relative to comparison conditions. Significant heterogeneity was found for the effect of nature on positive affect, and type of emotion assessment, type of exposure to nature, location of study, and mean age of sample were found to moderate this effect. The implications of these findings for existing theory and research are discussed, with particular emphasis placed on potential avenues for fruitful future research examining the effects of nature on well-being.