Pediatric surgery is a stressful operation for mothers and leads to increased anxiety and decreased self-efficacy in childcare. The current study was done to study the effect of providing required training to mothers of children with surgery and its effect on mothers' anxiety. This study is a clinical trial type, and 60 mothers with children who are candidates for surgery were randomly assigned to two control and intervention groups in the children's educational and therapeutic center. Then psychological training and a stress management program were done for the intervention group. In this study, the tool for collecting mothers' information included the Spielberger Anxiety Questionnaire. According to the results, there was no significant difference between the two groups before the intervention, however, after the intervention, the level of anxiety in the intervention group was significantly decreased compared to the control group (P<0.01). The findings obtained from the covariance statistical test revealed a significant difference between the intervention group and the control group after and before the intervention (p<0.01). According to the results, mothers who were in the intervention group had less anxiety before the child's surgery compared to the control group. The obtained findings showed that the methods of providing proper training for mothers with children undergoing surgery could be used as an effective way to reduce mothers' anxiety.