The United Against Bullying Plus (UAB+) programme integrates two existing approaches: a whole-school anti-bullying approach; with targeted components for those most at risk of perpetrating and experiencing bullying. The programme was delivered by the Anti-Bullying Alliance (ABA) and Kidscape. The aim of the two-year UAB+ programme was to reduce bullying and improve whole-school anti-bullying practice. To evaluate the feasibility, acceptability, and evidence of promise of the UAB+ programme, a mixed- methods implementation and process evaluation was conducted in 17 secondary schools in England, including two special schools. All Year 8 pupils in participating schools were eligible to complete an online Pupil Bullying and Wellbeing Questionnaire, which was repeated when they were in Year 9. School administrative data, such as attendance data, were also collected. Implementation surveys were completed by programme delivery staff and school staff to capture delivery of the programme components. Feedback surveys were completed by school staff, pupils, and parents and carers after training sessions and workshops. A total of 32 pupils, 34 school staff, six delivery staff, and one parent took part in an interview or focus group exploring their perspectives and experiences of the programme. The evaluation ran from September 2023 to July 2025. The study was co-funded by the Education Endowment Foundation (EEF) and the Youth Endowment Fund (YEF) in ‘A Safe, Positive Place to Learn’ funding round. Overall, the findings suggest that the universal and whole-school elements of the programme demonstrate readiness for trial. Targeted components would benefit from adaptations, followed by additional piloting. Extended follow-up periods would also support a fuller assessment of longer-term effects on pupil outcomes, particularly where whole-school cultural change is needed for the programme to have an impact.