This study extends the Theory of Planned Behavior by incorporating moral norms and environmental concerns to investigate factors influencing tourists' biodiversity conservation behaviors in ecologically sensitive destinations. The extended TPB model examines environmental attitudes, subjective norms, perceived behavioral control, moral norms, and environmental concerns. Using a mixed-method approach, we surveyed 420 tourists in Shemiranat, Iran, testing seven hypotheses, followed by 45 in-depth interviews. The extended model improves predictive power, with moral norms and environmental concerns emerging as crucial factors. These variables and environmental attitudes and subjective norms predict conservation intentions, explaining 52% of the variance. Unexpectedly, perceived behavioral control negatively relates to intentions. Qualitative data reveal knowledge deficits and infrastructural limitations as key barriers to translating intentions into behaviors. The findings have important implications for destination management and policy development: (1) the need for enhanced environmental education programs incorporating moral responsibility, (2) the development of supporting infrastructure for conservation behaviors, and (3) the implementation of targeted communication strategies addressing environmental and moral aspects of conservation. This study presents one of the first mixed-method investigations using an extended TPB model to examine tourists' biodiversity conservation behaviors in an ecologically sensitive area of an emerging economy.