Background: Bullying is a widespread problem in schools. Although several effective school-based bullying intervention programmes have been developed to reduce bullying and victimisation, it has rarely been investigated whether intervention programmes are also effective in helping bully-victims. Purpose: This study investigates the effectiveness of the KiVa antibullying programme in reducing the prevalence of bully-victims, compared with those defined as "pure bullies" and "pure victims". Programme description: The KiVa antibullying programme is a national anti-bullying programme in Finland. It consists of "universal actions" targeting all the students through student lessons and virtual learning environments (e.g. anti-bullying computer games), and "indicated actions", i.e. tackling the acute bullying cases. The programme aims at reducing bullying and victimisation by changing the responses of bystanders witnessing bullying. Sample: The target sample consisted of 23,520 participants (age range 8-15 years) from 738 intervention classrooms and 647 control classrooms in 195 Finnish schools. There were 12,450 primary (grades 2-6, 52.9%) and 11,070 secondary (grades 8-9, 47.1%) school students. Design and methods: The pre- and post-test data were collected in two waves 12 months apart, always in the end of a school year. The KiVa intervention took place during one school year, i.e. nine months. The effects on bully-victims, as well as on pure bullies and pure victims, were examined by prevalence changes as well as two-level multinomial logistic regression analyses. Results: The prevalence changes of bully-victims in intervention schools, in comparison with control schools, were -8% and -41% when identified by self-reports and peer-.reports, respectively. Controlling for student gender, school level (primary/secondary) and pretest bullying/victimisation status, the odds of being a bully-victim after the intervention year were 1.51 (self-reports) and 1.63 (peer-reports) times higher for a student in a control school, in comparison with a student in an intervention school. Conclusions: Our findings suggest that KiVa is effective in reducing the prevalence of bully-victims, and these effects are comparable or even larger than the effects on pure bullies and pure victims. It is possible that intervention for bully-victims might not be more difficult than that for bullies and victims.