Self-esteem and peer bullying, which affect the academic success and psychological development of secondary school students, are increasingly becoming a serious problem. This study was conducted to examine the effect of the Self-Esteem Development Programme applied to secondary school students on self-esteem and peer bullying victimization. This randomized controlled trial was conducted with 66 students (intervention = 33, control = 33) studying in the 6th grade at a secondary school. Personal Information Form, Rosenberg Self-Esteem Scale and Peer Bullying Identification Scale Adolescent Form were used to collect the data. The intervention group received 8 sessions of Self-Esteem Development Programme in the form of one session per week of 45–60 min; the control group continued their routine education programme. In the study, after the Self-Esteem Development Programme, the mean self-esteem score of the intervention group increased and the mean peer bullying score decreased, and the difference between the groups was found to be statistically significant (p < 0.05). In conclusion, it can be stated that the Self-Esteem Programme is an effective psychiatric nursing intervention in increasing self-esteem and reducing peer bullying. Students with low self-esteem are at risk of exposure to peer bullying. This study provides significant evidence for improving the self-esteem and reducing peer bullying among students who are at risk due to low self-esteem and peer bullying. The results of this study demonstrate that the Self-Esteem Development Programme can be utilized to enhance self-esteem and reduce exposure to peer bullying among students. ClinicalTrials ID: NCT04737374. •Students with low self-esteem are exposed to more peer bullying.•The Self-Esteem Development Programme has improved students' self-esteem.•The Self-Esteem Development Programme has reduced peer bullying among students.