Bullying victimization is associated with sleep disturbance. The present study aimed to investigate the impact of bullying victimization on sleep disturbance, and the moderating effect of mindfulness on this association, also exploring differences across sex. A sample of 420 Chinese children (Mage = 9.60, SD age = 1.11, 48.10% girls) in grade 3 to grade 6 were recruited to complete the revised Bully/Victim Questionnaire, the Chinese version of Pittsburg Sleep Quality Index, the Child and Adolescent Mindfulness Measure, as well as the Family Affluence Scale. Results showed that bullying victimization was positively associated with sleep disturbance (β = 0.20, p < 0.001). And the effect of bullying victimization on sleep disturbance was moderated by mindfulness (β = -0.16, p < 0.001), and the effect was invalid for children with high mindfulness (β = 0.04, p > 0.05). Subgroup analyses indicated the buffering effect of mindfulness only existed among boys (β = -0.19, p < 0.01) but not girls (β = -0.11, p > 0.05), suggesting that mindfulness may buffer this association, mainly for boys.