Introduction: The presence of comorbidities modulates the aging process, the diagnosis of cancer can significantly compromise the health of the elderly, which affects their quality of life. Objective: Determine the association between the functional dependence and the quality of life in elderly oncology patients treated with radiotherapy. Methods: Retrospective analytical study, carried out in 181 outpatients of Centro Médico Naval del Callao, Perú, male, older than 60 years. The functional dependence was assessed with Barthel index and Lawton scale; and the quality of life was assessed with World Health Organization Quality of Life-Older Adults Module (WHOQoL-Old). Results: A statistically significant association was found between functional dependence and quality of life, for both the basic activities of daily living (PR= 1.04 [IC 95 %: 1.01-1.07]), and the instrumental activities of daily living (PR= 1.08 [IC 95 %: 1.01 – 1.13]). Conclusion: There was significant association between the functional dependence and the poor quality of life in the elderly oncology patients treated with radiotherapy.