Introduction : Prostate cancer is the most common cancer in men over 65. Depression is frequent in this population but remains underdiagnosed, particularly due to atypical clinical presentations, confusion with treatment side effects, and sociocultural perceptions that trivialize the psychological distress of older adults. The objective of this study was to describe the obstacles to screening for depression in older patients treated for prostate cancer, analyze professional perceptions, and identify potential improvements to the care pathway. Methods : A qualitative study incorporating a clinical case of severe depression in a 76-year-old man treated with hormone therapy for prostate cancer, and semi-structured interviews conducted with a university hospital geriatrician and a geriatric psychiatrist. Results: Psychological vulnerability is increased by the cancer diagnosis, the loss of virility associated with treatment, geriatric frailty, and social isolation. Screening practices remain inconsistent: geriatricians used standardized tools, while psychiatrists intervened after the disorder had already developed. Identified obstacles included confusion between depressive symptoms and side effects, persistent taboos surrounding psychiatry, a lack of interdisciplinary coordination, and the absence of institutional protocols. Professionals agreed on the need for a structured screening protocol, targeted training, and interdisciplinary collaboration. Analysis of the literature and professional guidelines reinforced the need to implement a proactive screening approach, particularly at the initiation of hormone therapy. Conclusion : This study highlighted the need for a preventive and integrative approach to identify depression early in this high-risk population. Systematizing screening, adapting tools to the cultural context, and fostering collaboration among professionals working with older adults are essential to improving their quality of life and preventing suicidal complications.