Introduction: Child bullying has been one of the forms of violence considered by national and international institutions. The problems behaviors of the child are effective in reducing the Mother's sense of competence. The sense of competence has a great impact on the quality of the parent-child relationship. This study aimed to compare the effectiveness of the two Parenting training programs Supportive Parenting and Leading by Modeling on the Parenting Sense of Competence of mothers with a bully son. Methods: This study employed a quasi-experimental method using a pretest-posttest design with a control group and a three-month follow-up. The research population included all primary schools for boys (8-10 years old) in District 4 of Tehran in 2020. The participants were selected using voluntary convenience sampling and were randomly assigned to three groups. Finally, 60 mothers whose sons scored higher on the Illinois Bullying Scale were selected as the participants and divided into three groups of 20 (two intervention groups and one control group). The instruments used to collect the data were the Illinois Bullying Scale (Espelage & Holt, 2001), the Parenting Sense of competence scale (Gibaud-Wallston et al. 1978) The participants in both intervention groups attended Supportive Parenting and Leading by Modeling training programs for Thirteen two-hour sessions once a week. The collected data were analyzed using repeated-measures analysis of variance (ANOVA) with SPSS software (V. 22). Results: The findings showed a significant difference between the intervention and control groups in Parenting sense of competence (P=0. 0001) in the post-test and follow-up phases. While there was a significant difference between the effectiveness of the two programs on the Parenting sense of competence and the Parenting Leading by Modeling program (47. 35 ± 8. 10, P <0. 001) was more effective than the supportive Parenting program (39. 60 ± 9. 15, P <0. 001). Conclusions: The results showed that both support and leading by modeling programs are effective in improving the sense of competence of mothers. It seems that training mothers with a bullied son can help reduce mothers› psychological stress and improve their relationships with their children.