The current study aims to test the hypotheses that are central to Karasek's Job Demand Control Model in relation to workplace bullying. Particular contributions are, first, the focus upon both targets and perpetrators of workplace bullying, and second, the two-wave design with a 6-month time lag. We assume that (a) workload at Time I associates positively with being a target/perpetrator at Time 2, (b) job autonomy at Time 1 associates negatively with being a target/perpetrator at Time 2, and (c) the positive relationship between workload at Time 1 and being a target/perpetrator at Time 2 is stronger under the condition of low (vs. high) job autonomy at Time 1 (i.e., interaction between workload and job autonomy). Moderated hierarchical regression analyses (N = 320) revealed lagged main effects for being a target, and interaction effects for being a perpetrator. In particular, Time 1 workload was positively and Time 1 job autonomy negatively associated with being a target at Time 2. Job autonomy at Time I reduced the positive relationship between workload at Time 1 and being a perpetrator at Time 2. Overall, our results suggest that high strain jobs relate to both being a target and to being perpetrator of workplace bullying, yet through different processes: main effects and interactions, respectively.