Background: It is well established that older patients with cancer have a significantly higher risk of suicide. However, a comprehensive understanding of the risk factors is lacking. In this study, we aimed to identify groups at an increased risk of suicide among patients aged ≥75 years with a previous cancer diagnosis. Material and methods: All Polish individuals diagnosed with cancer at the age of ≥75 years between 1 January 2009 and 31 December 2019 were included in this study. Standardized mortality ratios (SMRs) and 95 % confidence intervals (CIs) were calculated. Results: A total of 410,440 patients (211,730 men and 198,710 women) were included in this study. SMR for both sexes was 1.64 (95 % CI 1.43-1.87). When analyzed by sex, a significantly higher risk was observed only in men (SMR 1.70, 95 % CI 1.47-1.95). Among them, the risk of suicide was observed after the diagnosis of lymphoma (2.83, 1.14-5.82), lung cancer (2.63, 1.70-3.89), kidney cancer (2.16, 1.03-3.96), colorectal cancer (1.96, 1.41-2.65), urinary tract cancer (1.86, 1.22-2.70), and prostate cancer (1.40, 1.07-1.82). The highest risk of suicide in men was observed within 6 months of diagnosis (2.83, 2.11-3.71). Conclusions: Men diagnosed with cancer at ≥75 years of age are at a higher risk of suicide than men of the same age in the general population. The observations from this study suggest which are the most vulnerable groups of elderly patients with cancer, and the time at which they should be given special support.