The process of psychological adjustment to breast cancer was examined at diagnosis and at 3- and 6-month follow-ups in a sample of 80 women with Stage I-Stage IV breast cancer. At diagnosis, symptoms of anxiety/depression were predicted by low dispositional optimism, and this path was partially mediated by use of emotion-focused disengagement coping. Younger age also was predictive of anxiety/depression symptoms at time of diagnosis, and this relationship was fully mediated by magnitude of intrusive thoughts. At 3 months, changes in anxiety/depression symptoms were predicted only by intrusive thoughts. At 6 months, low dispositional optimism reemerged as a significant predictor of changes in anxiety/depression and again was partially mediated by the use of emotion-focused disengagement coping. Independent effects for problem-focused engagement and disengagement and emotion-focused engagement coping were also found at 6 months. Implications of these data for psychosocial interventions with breast cancer patients are highlighted.