Nature-based education, characterized by authentic contexts and experiential learning, has increasingly been recognized as a potentially effective educational approach for fostering sustainable development literacy among university students. This study aimed to examine the influence of nature-based education on university students’ sustainable development behavior. It further investigated the sequential mediating roles of sustainability knowledge and attitudes. A cross-sectional self-administered questionnaire survey was conducted among 1248 university students across 21 prefecture-level cities in China. Data were analyzed using SPSS (Version 28.0) and SmartPLS (Version 4.0). Partial least squares structural equation modeling (PLS-SEM) was employed to test the hypothesized model and assess the relationships among latent constructs. The results indicated that nature-based education was positively associated with sustainability knowledge (β = 0.337, p < 0.001) and, to a lesser extent, sustainability attitudes (β = 0.106, p < 0.01), but had no significant direct effect on sustainable development behavior. Instead, sustainability attitudes mediated the knowledge–behavior relationship, while sustainability knowledge and attitudes jointly formed a significant sequential mediation pathway.