Even though school principals have many responsibilities, dealing with destructive behavior such as bullying among students is something that cannot be avoided. Scant attention has been paid especially to sources of influence on school principalâ€™s self-efficacy regarding to dealing with bullying and what actually is their ability when they deal with this type of problem. The purpose of this study is to identify the overall source of influence that contributes to school principalâ€™s self-efficacy and what are the levels of their self-efficacy in terms of dealing with bullying in secondary schools. Responses to sources of influence and their sense of efficacy when dealing with bullying among students in secondary schoolswere sought from 428 in-serviceÂ school principals across Malaysia by sending (mailed) questionnaires to respective respondents. Based on the result of this study the level of school principalsâ€™ self-efficacy in terms of dealing with bullying in secondary school was moderate. AlthoughÂ there is no documented record of local research that examine the sources of influence onschool principalsâ€™ self-efficacy in dealing with bullying among students, one clear finding that arises from this study is that, mastery experience is prominent predictor ofschool principals self-efficacy in dealing with bullying among students in secondary schools. ThisÂ result is in line with Banduraâ€™s finding (1977, 1997) where he had identified that mastery experience as the most important determinant ofÂ self-efficacy.Should there any developmental program for school principalÂ regarding the issue of bullying among students in secondary schools, it is recommended that it should explicitly address this particular source ofÂ influence with specific types of training and educational experiences that focus on mastery building through cognitive and meta cognitive strategies as well as cultivating self-regulation competencies.