This study examines the determinants of ethical behavior intention among purchasing executives in multinational corporations (MNCs) in Malaysia. Employing a quantitative approach and drawing upon the theory of planned behavior (TPB), the study investigates the influence of attitudes, perceived behavioral control, and subjective norms on ethical behavior intention, as well as the moderating effect of religiosity based on a usable sample size of 307 purchasing executives. Findings reveal that attitudes and perceived behavioral control positively influence ethical behavior intention, while subjective norms do not exhibit significant impact. Religiosity emerges as a significant moderator, strengthening the relationship between attitudes and perceived behavioral control with ethical behavior intention. However, religiosity does not moderate the influence of subjective norms. Theoretical implications highlight the continued salience of TPB dimensions especially attitude and perceived behavioural control which are part of an individual’s psychological factors in influencing ethical behaviour intentions. The integration of religiosity into the TPB framework was also a meaningful addition in better comprehending its indirect effect in a multi-religious country setting; a phenomenon that has not been explored to a great extent by TPB scholars thus far. Practically, the study contributes towards improved understanding of ethical behavior intention in MNC settings, emphasizing the role of individual religious beliefs and contextual factors.