Green exercise is physical activity that takes place in the presence of natural environments. Despite the promising evidence of the benefits, little is known about how individuals' thoughts and feelings influence participation in green exercise and subsequent outcomes. The aim of the current research was to develop questionnaires using the Theory of Planned Behaviour as a framework that could both directly and indirectly assess attitudes, subjective norms and perceived behaviour control, along with intention toward green exercise. Confirmatory factor analyses confirmed that the indirect, direct, and intention measures all had good overall model fits when tested on a refinement (n = 253) and validation (n = 230) sample. The questionnaires will contribute towards helping to better understanding individuals' beliefs about green exercise, how these influence behaviour, and ultimately to enable the development of effective interventions promoting green exercise.