Introduction: Since nurses and nursing students interact with culturally diverse clients in health care settings, training programs are required to improve cultural competence and self-efficacy among them. This study aimed to investigate the effect of an online cultural care training program on cultural competence and self-efficacy among postgraduate nursing students. Methods: The present interventional study used random sampling to allocate 80 postgraduate nursing students into the intervention and control groups. Cultural care training program was held for the intervention group. Results: No significant difference in cultural competence and self-efficacy scores was found between the intervention and control groups in the pretest. However, the intervention group scored higher in terms of cultural competence and self-efficacy after the intervention. Discussion: Given cultural diversity and prevalence of medical tourism, nursing instructors need to pay special attention to cultural care education at all academic levels.