This study investigates the relationships between eco-anxiety, social capital, locus of control, and pro-environmental behaviour among young adults. As environmental crises intensify, understanding the psychological and social factors that drive sustainable actions has become increasingly crucial. A convenience sample of 381 young adults aged 18–25 was used. Data were collected through validated scales, including the Hogg’s Eco-Anxiety Scale, the Short Social Capital Assessment Tool (SASCAT)-Indian Version, Rotter’s Locus of Control Scale, and the Pro-Environmental Behaviour Scale. The findings revealed significant positive correlations between eco-anxiety and pro-environmental behaviour (ρ = 0.275), social capital and pro-environmental behaviour (ρ = 0.430), and a weak but significant correlation between locus of control and pro-environmental behaviour (ρ = 0.128). Regression analysis indicated that eco-anxiety had the strongest predictive impact on pro-environmental behaviour, accounting for 24.4% of the variance, while social capital and locus of control did not significantly mediate this relationship. These results suggest that emotional responses, such as eco-anxiety, play a pivotal role in motivating sustainable actions and hence empowering young minds, whereas social and cognitive factors may require further investigation. The study reinforces the importance of designing interventions and policies that harness growth and emotional engagement to promote green behaviour while addressing potential barriers related to social unity and cognitive factors. By integrating emotional, social, and cognitive perspectives, this research sheds light on the underlying mechanisms that drive sustainable behaviour, hence offering valuable insights for future studies and interventions aimed at fostering environmental engagement among young adults.