This study explores the relationship between adjustment to cancer and quality of life in a sample of 68 newly diagnosed non-metastatic breast cancer patients. Responses were assessed on three occasions following communication of the diagnosis and included the Mental Adjustment to Cancer (MAC) scale, a measure of denial and a Spanish quality of life questionnaire for breast cancer patients. Appropriate medical variables were considered and included in the analysis. MAC subscales showed adequate internal consistency; nevertheless, there was overlap between subscales and a second order factorial analysis suggested that two dimensions (‘perceived threat’ and ‘perceived control’) suffice to describe mental adjustment to cancer. A strong association was found between mental adjustment to cancer and reported vague physical symptomatology at the first assessment. Older patients showed higher ‘Denial’ scores and lower scores for ‘Anxious preoccupation’. ‘Fighting spirit’ and ‘Denial’ were associated with better present and future quality of life; ‘Helpless/hopeless’, ‘Anxious preoccupation’ and ‘Fatalism’ responses were negatively correlated with well-being. These results are discussed from a theoretical point of view.