Purpose: To determine effects of family conflict mitigation documentary programs on conflicts, autonomic nerve activation (ANA), and happiness of elderly in long-term care hospitals. Methods: This study used a non-equivalent control group with a pretest-posttest design. It was conducted on 39 elderly patients (19 in the experimental group and 20 in the control group) in long-term care hospitals. The experimental group (n= 19) received family conflict mitigation documentary programs. The family conflict mitigation documentary programs consisted of four sessions (40-50 minutes per session). These programs were implemented in small groups, with each group having five elderly. Data were analyzed by sing the conflict checklist, the Oxford Happiness Questionnaire, Chi-square test with Fisher’s exact test, independent t-test, paired t-test, and repeated measure ANOVA using the SPSS/WIN 21.0 program. Results: The participants in the experimental group showed significantly decreased scores of conflict (t= -2.31, p= .028) and the value of sympathetic nervous system activity (t= 8.36, p= .007) compared with those of the control group. The participants in the experimental group showed significantly increased the value of parasympathetic nervous system activity (t= -2.91, p= .008) and scores of happiness (t= 5.46, p< .001). Conclusion: The family conflict mitigation documentary programs on conflicts, ANA, and happiness of the elderly in long-term care hospitals are effective intervention programs for mitigating conflicts between elderlies and their families and for improving happiness of the elderly in long-term care hospitals.