Against the backdrop of increasing interest in the relationship between Nature and health, this study examined the effect of perceived environment type and indicators of perceived environmental quality on short-term emotional well-being following outdoor group walks. Participants (n = 127) of a national group walk program completed pre- and post-walk questionnaires for each walk attended (n = 1009) within a 13-week study period. Multilevel linear modelling was used to examine the main and moderation effects. To isolate the environmental from the physical activity elements, analyses controlled for walk duration and perceived intensity. Analyses revealed that perceived restorativeness and perceived walk intensity predicted greater positive affect and happiness following an outdoor group walk. Perceived restorativeness and perceived bird biodiversity predicted post-walk negative affect. Perceived restorativeness moderated the relationship between perceived naturalness and positive affect. Results suggest that restorative quality of an environment may be an important element for enhancing well-being, and that perceived restorativeness and naturalness of an environment may interact to amplify positive affect. These findings highlight the importance of further research on the contribution of environment type and quality on well-being, and the need to control for effects of physical activity in green exercise research.