The effectiveness of the Viennese Social Competence (ViSC) programme on various bullying-related teacher variables was examined at two time points with a quasi-experimental intervention-control group design. In Austria, Cyprus, and Turkey, teachers participated in a series of in-school trainings and implemented an anti-bullying prevention programme in their schools for one year. At pre-test, 767 teachers (515 in the intervention and 252 in the control group) and at post-test 665 teachers (464 in the intervention and 201 in the control group) rated their perceived knowledge and competence, and the likelihood of using different interventions in a hypothetical bullying scenario. For pre-test and post-test data, two 3 (country) x 2 (intervention) MANOVAs were conducted. Findings showed that Cypriot teachers profited the most from the anti-bullying programme, while Austrian and Turkish teachers profited comparatively less. High-quality basic teacher education in addition to in-school trainings within anti-bullying programmes is an essential component to prevent bullying in schools.