Psychiatric nurses face moral dilemmas that affect their mental health. We investigated whether sense of coherence (SOC) buffers psychiatric nurses' perceived effects of moral dilemmas on their psychological distress. A total of 418 nursing professionals in 6 psychiatric hospitals in Japan completed self-administered questionnaires. A negative correlation was observed between "patient rights" (r = -0.24, p < 0.001), "relationships other than patient" (r = -0.28, p < 0.001), "nursing care" (r = -0.25, p < 0.001) of moral dilemmas and "manageability" of SOC. Additionally, a negative correlation was observed between "patient rights" (r = -0.22, p < 0.001), "relationships other than patient" (r = -0.21, p < 0.001) of moral dilemmas and "comprehensibility" of SOC. Hierarchical multiple regression analysis used the Kessler Psychological Distress Scale-10 (K10), which assessed the degree of mental distress, as the dependent variable, and moral dilemmas and SOC as the independent variables, along with their interaction terms. The K10 scores significantly changed depending on the degree of moral dilemmas in the low SOC group, but not in the high SOC group. SOC buffers the effects of psychiatric nurses' perceived moral dilemmas on their psychological distress.