BACKGROUND Causes of death (CODs) in patients with gastric cancer (GC) need to be studied. We examined the cancer-specific and non-cancer deaths among patients diagnosed with GC from 1975 to 2019. MATERIAL AND METHODS We obtained medical records from the Surveillance, Epidemiology, and End Results (SEER) database. We used SEER*Stat software to calculate standardized mortality ratios (SMRs) for specific CODs and performed a competing risk analysis to evaluate the cumulative mortality of specific CODs. RESULTS The final study cohort included 42 813 patients with GC, with a mean age at diagnosis of 67.7 years. As the end of 2021, a total of 36 924 (86.2%) patients died. Of these deaths, 24 625 (66.7%) were from GC, 6513 (17.6%) were from other types of cancers, and 5786 (15.7%) were from non-cancer causes. The most prevalent non-cancer CODs were heart diseases (2104; 5.7%), cerebrovascular diseases (501; 1.4%), and pneumonia/influenza (335; 0.9%). Among patients who survived over 5 years, non-cancer causes surpassed GC as the main CODs. Patients with GC had a higher risk of dying from many non-cancer causes than expected in the general population, particularly from suicide (SMR, 3.03; 95% CI, 2.35-3.85) and septicemia (SMR, 2.93; 95% CI, 2.51-3.4). The competing risk analysis showed that the cumulative mortality of GC gradually declined with a more recent diagnosis. CONCLUSIONS Although GC was the leading COD among patients with GC, non-cancer CODs accounted for a substantial number of deaths. These findings provide useful guidance on potential death risks among patients with GC.