Background Caring behaviour is critical for nursing quality, and the clinical internship environment is a crucial setting for preparing nursing students for caring behaviours. Evidence about how to develop nursing students’ caring behaviour in the clinical environment is still emerging. However, the mechanism between the clinical internship environment and caring behaviour remains unclear, especially the mediating role of moral sensitivity and the moderating effect of self-efficacy. Research objective This study aimed to examine the mediating effect of moral sensitivity and the (...) moderating function of self-efficacy on the association between the clinical internship environment and caring behaviours. Research design A cross-sectional design used acceptable validity scales. The hypothesised moderated mediation model was tested in the SPSS PROCESS macro. Participants and research context This survey collected data from 504 nursing students in an internship at a teaching hospital in Changsha, China. Ethical considerations This study was pre-approved by the ethics committee of the medical school (No. E2022210). Informed consent was obtained from all students. Results The clinical internship environment ( B = 0.450, 95% CI = [0.371, 0.530]) and moral sensitivity ( B = 1.352, 95% CI = [1.090, 1.615]) had positive direct effects on nursing students' caring behaviours. Clinical internship environment also indirectly influenced students’ caring behaviours via moral sensitivity ( B = 0.161, 95% CI = [0.115, 0.206]). In addition, self-efficacy played a moderating role between the clinical internship environment and caring behaviours ( B = 0.019, 95% CI = [0.007, 0.031]), as well as the relationship between the clinical internship environment and moral sensitivity ( B = 0.006, 95% CI = [0.003, 0.010]). Conclusion Moral sensitivity mediates the effect of the clinical internship environment on caring behaviour, and self-efficacy strengthens both direct and indirect effects. This study emphasises the importance of self-efficacy in developing moral sensitivity and caring behaviours in nursing students. (shrink)