Objective: To investigate the incidence and clinical characteristics of urothelial carcinoma (UC) accompanied with multiple primary carcinoma (MPC). Methods: The clinical data of 121 UC patients with MPC in Peking University Third Hospital from January 2010 to May 2018 were retrospectly analyzed. Results: UC patients with MPC accounted for 9.74% (121/1 242) of all the UC patients. The ratio of male to female patients was 2.10∶1 in the total MPC patients, but it was 1∶1 in the upper urinary tract MPC subgroup. The MPC patients were more common in elderly people, whose medium age was 68 (32-93) years old. Of all the location (131 person-time) of other tumors besides UC, the digestive system tumors occurred most frequently, accounting for 41.98% (55/131), followed by the urinary and male reproductive system tumors (20.61%, 27/131) and the female reproductive system (12.21%, 16/131). The proportion of the digestive system tumors (47.37%, 9/19) was the highest in the upper urinary tract MPC, with a total number of the other primary cancer of 19 person-time. However, the proportion of the urinary and male reproductive system tumors (37.14%, 13/35) was higher in the synchronous MPC group, with a total number of the other primary cancer of 35 person-time. Some patients had a history of radiotherapy and/or chemotherapy before UC was diagnosed. We also observed 2 cases of genetically confirmed Lynch syndrome. The median overall survival (mOS) of UC patients with MPC was 132 months, and the mOS of patients with UC as the first malignancy (including synchronous MPC and UC as the first malignancy in metachronous MPC) was 120 months. The mOS of the synchronous MPC group was 84 months, which was significantly shorter than 178 months of metachronous MPC group (χ(2) =14.029, P<0.001). Conclusions: The incidence of UC accompanied with MPC is not low, and the most common sites of MPC are the digestive system and reproductive system. Therefore, screening for MPC in UC patients, especially those with personal or family history of tumors, as well as elderly patients, may help early diagnosis and treatment of MPC patients and improve their prognoses.