<p>It is challenging to tackle bullying in secondary education, because (1) bullying is less direct and visible than in primary education, (2) bullying is rewarded with more status in adolescence, (3) adolescents have an increased need for autonomy and therefore are less likely to follow teacher instructions, and (4) the school culture is more complex. A new anti-bullying program, GRIPP (GRoup forming, Identity, and bullying Prevention Program), attempts to tackle those challenges. The present study aims to provide insights into the feasibility of the program during one school year, including information on the experiences of homeroom mentors and students with the intervention. Teachers’ feedback in portfolios (<i>N</i> = 141) on their experience with the materials, preparation time, number of lessons delivered, and lesson delivery suggested that the GRIPP anti-bullying program was appropriate for the adolescent target audience, with teachers evaluating the materials easy to use. Multilevel analyses on quantitative student data in a convenience sample (because of Covid-19) indicated that there were no differences between the intervention (<i>N</i>_students = 644, <i>N</i>_classrooms = 56) and waitlist (<i>N</i>_students = 243, <i>N</i>_classrooms = 26) group on self-reported bullying and victimization in our sample. Further research on the school culture within secondary education, and the readiness to implement and evaluate a school-wide intervention, is needed before an intervention such as the GRIPP program can successfully be disseminated. This study indicates that when teachers have enough resources to implement GRIPP, they consider the program feasible for implementation. Further testing is necessary to measure the program’s effectiveness.</p>