This is a cross-sectional study that analysed the association between workplace bullying and LBP. The participants were 894 judicial civil servants from Porto Alegre, southern Brazil. Workplace Bullying was measured by the Negative Acts Questionnaire (NAQ-r) and Low Back Pain by the Nordic Questionnaire for Musculoskeletal Symptoms (NQMS). Logistic Regression was used to analyse data and test hypotheses. The prevalence of LBP in the last 7 days was 50.1%, while the overall prevalence of Chronic LBP was 19.3%. Some psychosocial factors at work were strongly associated with both outcomes. Workplace bullying was strongly associated with LBP, even after adjustment for several covariates. The odds of LBP in the last 7 days among bullied workers was 1.89 (95% CI: 1.31-2.71) times higher, compared to non-bullied. Workplace bullying was also associated with chronic LBP after adjustment for sociodemographic, behavioural and some occupational factors (OR = 1.60; 95% CI: 1.05-2.44). Psychosocial factors at work, and particularly workplace bullying, were strong risk factors for LBP, in contrast to most individual factors, and dose-response patterns were showed. Positive associations between bullying and LBP raise hypotheses on causation, and the role of psychosocial factors at work are discussed. Further longitudinal studies should address these hypotheses, investigating causal paths, mechanisms and possible mediation. PERSPECTIVES: As a psychosocial risk, workplace bullying may play a role in low back pain and can be focus of interventions to prevent LBP. Dose-response patterns on the association between workplace bullying and low back pain are discussed and hypotheses are raised. The paper addresses different ways of measuring and categorising bullying at work, in order to study the relationship between bullying and pain.