BackgroundMost research on workplace bullying has examined the impact of the mistreatment on those exposed. Although bullying also is assumed to have significant ripple effects on bystanders, the empirical evidence for this line of research is highly fragmented and inconclusive. The overarching aim of this planned systematic review and meta-analysis is therefore to determine whether witnessing bullying of others at the workplace is associated with health problems and lower well-being among the observers. To achieve this aim, the review includes an assessment of which theoretical frameworks and methodological designs used in research so far and shed light on which confounders, mediators, and moderators that have been accounted for.MethodsA systematic review and meta-analysis will be conducted. Electronic databases will be searched using pre-defined search terms to identify relevant studies. Eligible studies should report empirical findings on any individual outcome variable assessed among witnesses to workplace harassment and bullying or any overlapping concept. Primary observational studies with cross-sectional or prospective research design, case–control studies, and studies with experimental designs will be included. Qualitative interviews and case studies will be excluded. The methodological quality of the included studies will be assessed with a previously established checklist for studies on workplace bullying. The quality of evidence for an association between witnessing bullying and potential outcomes will be evaluated in accordance with the GRADE system. A random effects meta-analysis will be conducted with the Comprehensive Meta-Analysis software, version 3.DiscussionWe expect that findings on outcomes of bystanding to workplace bullying will provide practitioners with an understanding of the effects workplace bullying may have also on non-targets and the workplace as a whole. Such information is important regarding the development and implementation of effective measures and interventions against bullying. In addition, the review will increase our understanding of existing research gaps and enable us to make recommendations to address them. Our work aligns with the sustainable development agenda to protect workers and reduce inequalities at the workplace.Systematic review registrationPROSPERO 342006.