This study investigated the correlates of acute stress disorder (ASD) following a diagnosis of cancer. Adults diagnosed with first onset head, neck, or lung malignancy (N = 82) were assessed within one month of diagnosis using the ASD Interview, and the Structured Clinical Interview for DSM-IV to index the incidence of ASD and other affective disorders following their cancer diagnosis. Participants were also administered questionnaires that assessed dissociative symptoms, coping strategies, and quality of life. Acute stress disorder was diagnosed in 28% of participants. Acute stress disorder severity was associated with gender, elevated dissociative responses, trait anxiety, and preoccupation with one's diagnosis, and a decline in cognitive functioning. This study provides evidence for identifying recently diagnosed cancer patients who may benefit from psychological assistance.