Multiple primary cancer is defined as two or more cancers in a single patient. Although the presence of bladder and prostate carcinoma in the same patient is not a rare event, third primary malignancy in patients with bladder and prostate carcinoma is rare. In this report, we present a patient who developed synchronous multiple primary cancers including bladder, prostate and thyroid papillary cancer within a five-month period. This combination of synchronous multiple primary carcinomas, according to the best our knowledge, has never been reported in the literature. In conclusion, the possibility that multiple primary malignancies exist must always be considered during pretreatment evaluation. The focal thyroid 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography / computed tomography incidentaloma with high standardized uptake values warrants a pathological diagnostic procedure.