Sustainable development education (SDE) plays a critical role in equipping young learners to address contemporary environmental challenges. While environmental knowledge remains central to sustainability education, growing research highlights the importance of psychological variables in shaping pro-environmental behaviour. The present study examined the influence of cognitive factors (environmental knowledge) and emotional factors (empathy toward nature, emotional regulation, and eco-anxiety) on sustainable behaviour among higher secondary students in Thrissur District, Kerala, India. A descriptive survey design was employed. The sample consisted of 300 students aged 16–18 years selected through stratified random sampling from government, aided, and private schools. Data were collected using three researcher-developed instruments: the Environmental Knowledge Scale (EKS), the Environmental Emotional Engagement Inventory (EEEI), and the Eco-friendly Behavioural Practices Checklist (EBPC). Reliability coefficients ranged from .78 to .89. Data were analysed using descriptive statistics, Pearson’s correlation, and multiple regression analysis.

Results indicated that environmental knowledge (r = .75, p < .01), empathy toward nature (r = .68, p < .01), and emotional regulation (r = .60, p < .01) were positively associated with sustainable behaviour. Eco-anxiety showed a significant negative correlation (r = −.42, p < .01). Regression analysis revealed that cognitive and emotional factors jointly explained 62% of the variance in sustainable behaviour (R² = .62, F(4, 295) = 120.45, p < .001). The findings underscore the need to integrate socio-emotional learning and experiential strategies into sustainability education. The study contributes to environmental psychology literature by highlighting the combined predictive power of cognition and emotion in adolescent sustainability behaviour within the Indian educational context.