Purpose Based on dual-system theory, this study aims to reveal the mediating mechanisms of green consumption behaviour influencing sustainable green consumption behaviour. Design/methodology/approach This study collected three-wave data (N = 959) to test the hypotheses. Findings The results showed that green consumption behaviour affects sustainable green consumption behaviour through two mediating mechanisms: a habit-based mechanism and a psychological benefits-based mechanism. In addition, these two mechanisms jointly promote sustainable green consumption behaviour. Originality/value This study is a pioneer in focusing on sustainable green consumption behaviour and identifies two mediating mechanisms of green consumption behaviour affecting sustainable green consumption behaviour. It enriches the literature on green consumption and sustainable green consumption in retail.