In this study the causal relationships between work characteristics, in terms of job demands and job resources, and both targets' and perpetrators' reports of workplace bullying, are investigated. In line with the Job Demands-Resources model and the bullying literature, we assumed that both high job demands (i.e. workload, role conflict and job insecurity) and low job resources (i.e. task autonomy, social support and skill utilization) increase bullying over time (i.e. normal causation). Our sample included 177 employees of various establishments of a large Belgian organization. The results of structural equation modelling analyses partially supported our hypothesis. As expected, we found that T1 job demands related positively to targets' reports of bullying at T2 one year later, and that T1 job resources related negatively to T2 targets' reports of bullying. Unexpectedly, there was no significant cross-lagged effect of T1 job demands and resources on T2 perpetrator's reports of bullying. No evidence was found for reverse causation or reciprocal effects. Overall, at least for targets, these findings support the validity of the theoretical models postulating a causal link from work characteristics to workplace bullying.