Changing behaviours responsible for environmental harm may be perceived as an impediment to human well-being, leaving individuals and institutions hesitant to take action. However, largescale survey data suggest that those who engage in more pro-environmental behaviour are more likely to report greater subjective well-being. The present study was the first (to our knowledge) to experimentally manipulate pro-environmental behaviour in order to assess its causal effects on affect and meaning in life. Participants (N = 343) were randomly assigned to either 1) a group who chose and engaged in a pro-environmental behaviour from a provided list of options; or 2) a control group who found and photographed public art from a provided list of options. In order to determine whether pro-environmental behaviour had an effect on meaning in life and affect over and above that of the control group, post-activity measures were compared between groups. The analyses found that there were no significant differences between the pro-environmental group and the control group, and all pre-registered hypotheses were unsupported. Exploratory analyses revealed a within-participants effect, whereby both conditions produced a significant effect on positive and negative affect, as well as meaning in life when compared to participants' average over the last four weeks. Negative affect was most substantially mitigated in both conditions (ds = 0.91 -1.05). Trait-by-condition interactions were also explored. This study provides insight into the potential emotional effects of pro-environmental behaviour. However, given that all findings were exploratory, the results should be considered speculative and can serve as direction for future research.