This research aimed to investigate the effect of forgiveness training on mental health of mothers of children with behavioral disorder. The present study was an experimental research by pre-test, post-test design with control group. The study sample included 32 mothers of children with behavioral disorder who were selected by random sampling method from elementary schools of Tehran city and randomly assigned to experimental and control group (each consisted of 16 individuals). The experimental group participated in 8 forgiveness training sessions (two sessions weekly; each lasted for 60 minutes), while control group did not participate in these sessions. The research tool used in present study was Goldberg and Hiller's General Health Questionnaire. Data were analyzed using multiple analysis of covariance through SPSS version 23. The findings of this research showed that there was significant decrease in mean scores of general health problems (somatic symptoms, anxiety, social dysfunction and depression) in experimental group after the intervention in comparison with control group (p < 0.0001). The forgiveness training led to improvement of the mental health of mothers of children with behavioral disorder. Therefore, specific educational and rehabilitation program is needed in order to increase general health of mothers of children with behavioral disorder.