The location-based game (LBG) Pokémon GO remains one of the most successful and widely studied video games of recent years. Designed for outdoor play, LBGs have been associated with increased physical activity and environmental awareness beyond the game context. This study examines how specific game design features in Pokémon GO are associated with players' self-reported sustainable behaviours. Drawing on a motivational framework that categorises design features into the dimensions of achievement, immersion, and social engagement, we analysed online survey data from 303 players. Results showed that (a) only immersion-related features were positively associated with self-reported positive sustainable behaviours, and (b) no significant relationships were found between the motivational dimensions and negative sustainable behaviours. Further analysis indicated that participants' country of residence was a significant factor and that the design feature reminders, cues, and notifications accounted for the positive association within the immersion category. Our findings highlight how immersive, human-centred design features may align with sustainability-oriented dispositions, offering new insights into the interplay between game experiences and sustainability values.