The factors contributing to aggressive behaviours among individuals with intellectual disability (ID) are not fully understood. The goal of the present study was to examine whether vulnerability factors such as ID severity, speech, or motor impairments moderated gender differences in aggressive behaviours. Adults (n=296) with ID were recruited, and data on vulnerability factors and aggressive behaviours were collected through file reviews and interviews. Moderation analyses indicated that men were more likely to exhibit physical aggression than women, particularly those with a mild level of ID. Analyses also indicated that women were more likely to exhibit physical aggression than men, particularly those with speech impairment. Our findings suggest that gender-dependent vulnerability factors might contribute to aggressive behaviours among individuals with ID.