Objective: The Geriatric Depression Scale (GDS-15), a self-report questionnaire, emphasizes the psychological dimension of depression. We aimed to investigate whether GDS-15 scores were associated with mortality in older patients with cancer and describe the course of individual symptoms on the GDS-15. Methods: An observational, multicenter, prospective study of 288 patients 70 years or older with cancer followed over 24 months. The patients were assessed with the GDS-15 at inclusion, and after four and 12 months. An extended Cox regression model assessed the association between time-dependent GDS-15 scores and mortality. Results: After adjusting for cancer-related prognostic factors, a one-point increase in GDS-15 sum score increased risk of death by 12%. GDS-15 mean score increased during the first four months of the study, as did odds for the presence of the GDS-15 symptoms 'feel you have more problems with memory than most' , 'not feel full of energy' , and 'think that most people are better off than you' . The most prevalent and persistent GDS-15 symptom was 'prefer to stay at home, rather than going out and doing new things' , and 'not to be in good spirits most of the time' was the least prevalent. Conclusions: More severe depressive symptoms, as measured by the GDS-15, were associated with higher mortality in older patients with cancer. The importance of emotional distress and how to alleviate it should be investigated further in these patients.