The present study investigated the relationship between adult attachment style and depressive symptomatology in patients with HIV. Moreover, perceived social support was investigated as a potential mediator between adult attachment and depressive symptoms. A sample of 233 HIV-infected patients (90% male) completed questionnaires assessing adult attachment style (Relationship Questionnaire), depressive symptoms (Beck Depression Inventory), and perceived social support (Medical Outcomes Study Social Support Survey). After controlling for demographic and medical variables, an insecure adult attachment style was found to be strongly related with depressive symptoms. Half of the insecurely attached patients reported clinically elevated levels of distress, while one in nine securely attached patients reported elevated levels of distress (χ(2)=32.25, p=0.001). Moreover, the association between attachment style and depressive symptomatology was found to be partly mediated through perceived social support. This study strongly supports the notion that an insecure attachment style is a vulnerability factor for developing depressive symptoms that would warrant clinical attention when confronted with a chronic illness such as HIV. The clinical implications of these findings are discussed.