Introduction: Self-confidence in adolescents gradually diminishes during puberty due to changes in identity and in their responsibilities. It decreases more in adolescents suffering from chronic disease of diabetes, in whom promotion of self-confidence for self-management behaviors, has a significantly positive effect. The purpose of this study was to investigate the effect of spiritual care on the self-confidence of adolescents with type 1 diabetes. Materials and Methods: This quasi-experimental clinical trial study was performed on 52 adolescents with type 1diabetes, selected through convenience sampling and randomly assigned in two groups, the intervention and control (n=26 each). The intervention was implemented daily for 6 sessions in the experimental group. Data were collected using the demographic and Rosenberg scale and analysis was done by SPSS-19 software. Descriptive and inferential statistics and repeated measure ANOVA, Mann-Whitney, Fisher, and Chi-square tests were used. Results: The mean scores of self-confidence in the control group before/after the intervention, and also in the follow up period were 0.46, 1.5, and 1.46, respectively. The values in the intervention group were 3.92, 5.69, and 6.38, respectively. Results of analysis of variance showed the significant effects of intervention (p<0.001). Conclusion: The results indicate the effect of spiritual care on the self-confidence of adolescents with type 1 diabetes, emphasizing that nurses, as part of the health care system, must pay attention to spiritual care and its continuity in the care of these patients.