This study examines men's domestic aggression as a function of attachment insecurities, considering the mediating roles of the demand-withdraw communication pattern and relationship satisfaction. The sample included 55 Canadian men undergoing counseling for relationship difficulties including aggression. The men completed questionnaires assessing physical and psychological aggression, the two dimensions of attachment insecurity (anxiety over abandonment and avoidance of intimacy), the demand-withdraw communication pattern, relationship satisfaction, and social desirability (a control measure). As predicted, there was an association between attachment anxiety and aggression (both physical and psychological), which was mediated by the man demands/woman withdraws (MD/WW) pattern (as reported by the men). There was no evidence of mediation by the woman demands/man withdraws pattern, as reported by the men. Relationship satisfaction mediated the association between attachment anxiety and psychological (but not physical) aggression, but did not mediate the link between avoidance and aggression (physical or psychological). Limitations and clinical implications are discussed.