Objectives To examine the relationship between adverse childhood experiences (ACEs), workplace bullying victimisation and bullying behaviours to subordinates among Japanese workers.

Methods We conducted an internet-based cross-sectional survey among workers who had enacted 0, 1 and ≥2 types of bullying behaviours that had been directed towards subordinates in the past 3 years (n=309 for each group, total N=927). We assessed ACEs with questionnaires about adverse experiences at home and bullying victimisation at school. The total and controlled direct effects of ACEs on the number of bullying behaviours to subordinates were estimated from a baseline-adjusted and a direct-effect marginal structural ordinal logistic model, respectively.

Results There was a positive dose–response association between the level of ACEs and the frequency of workplace bullying victimisation, as well as the number of bullying behaviours enacted at work after adjustment for sex, age and childhood socioeconomic status (both p<0.001). Workers in the highest tertile of ACEs compared with the lowest tertile had 3.15 (95% CI 2.20 to 4.50) times higher odds of having perpetrated more bullying behaviours at work. The magnitude of the effect was 2.57 (95% CI 1.70 to 3.90) via pathways not mediated by workplace bullying victimisation in a direct-effect marginal structural model.

Conclusions People who had ACEs were at increased risk later in life of enacting bullying behaviours at work. Current findings may be useful to prevent bullying behaviours at work.