Research on effectiveness of workplace bullying interventions has lagged behind descriptive studies on this topic. The literature on bullying intervention research has only recently expanded to a point that allows for synthesis of findings across empirical studies. This study addresses the question of whether workplace bullying can be reduced in prevalence and consequences, if so to what extent and by which strategies and interventions. It opens with a brief overview of the nature of bullying at work and discussion of some precursors and existing interventions. However, its principal focus is on the findings obtained from selected (quasi-) experimental longitudinal studies on antibullying interventions, drawing together the results of studies conducted in Europe, USA, and Australia, including several economic sectors, and concerned about primary, secondary, and tertiary prevention programs and strategies. Additional emphasis is considered from the psychosocial drivers highlighted both from prescriptive and cross-sectional studies and factual empirical studies. One randomized control study and seven quasiexperimental longitudinal studies were identified by searching electronic databases and bibliographies and via contact with experts. The majority of outcomes evidenced some level of change, mostly positive, suggesting that workplace bullying interventions are more likely to affect knowledge, attitudes, and self-perceptions, but actual bullying behaviors showed much more mixed results. In general, growing effectiveness was stated as the level of intervention increased from primary to tertiary prevention. However, methodological problems relating to the evaluation designs in most studies do not allow direct attribution of these findings to the interventions. Overall, the evaluation of antibullying interventions must flourish and be improved, requiring close cooperation between practitioners and academics to design, implement, and evaluate effective interventions based on grounded theoretical and methodological approaches. Finally, this systematic review highlights future directions for enhancing the adoption, high-quality implementation, and dissemination of evidence-based workplace bullying prevention and intervention programs.