Primary bladder cancer is a frequent malignancy in the urology field, whereas secondary bladder neoplasms from a distant organ are extremely rare. This paper aims to report two rare cases of a secondary tumor of the urinary bladder from a primary gastric tumor and to perform a literature review of similar reported cases in order to better characterize its clinicopathological features and diagnosis in effort to shed light on this rare condition. The final diagnosis of secondary adenocarcinoma was made histologically after transurethral biopsy or resection of the bladder lesion. In one case, the bladder metastasis was a synchronous metastasis, and in the second case, it occurred under chemotherapy five months after initial diagnosis with gastric adenocarcinoma. Secondary adenocarcinoma of the bladder is extremely rare but should be considered when evaluating a bladder lesion in a patient treated for gastric cancer or presenting with gastric symptoms.