There is a lack of research into green exercise which investigates and compares motivational drivers between the different types of outdoor activities. The current paper addressed this gap by classifying and comparing three types of green exercise: (i) Recreational physical activity, (ii) competitive sport, and (iii) outdoor adventure sport. Using a mixed methodological approach, the present study investigated the motivations for adhering to green exercise and directly compared the differences between these three forms of green exercise. Online questionnaires and face-to-face interviews were used to collect data. The results demonstrated that within all types of green exercise, enjoyment was the greatest motivator. Based on analysis of the qualitative materials, extrinsic motivators such as the environment, family, and friends were highlighted as key factors in beginning and continuing their activity. However, intrinsic motivators were also emphasised as more important in adherence to green exercise. Furthermore, as seen in other research, numerous psychological benefits were reported over time. The results of the study may act as a starting point in understanding how we may increase public engagement in green exercise by prompting participants to select a form of green exercise that best suits them based on their motivational profile.