Bladder cancer is a common malignant tumor, and patients who have undergone radical cystectomy and urinary diversion require a lifelong abdominal stoma. This greatly affects their physiological, psychological, and social well-being. However, there is currently a lack of a self-assessment outcome scale specifically designed for bladder cancer patients with abdominal stomas. Therefore, we developed and validated a self-assessment outcome scale (PROS-BCAS) for Chinese bladder cancer patients with abdominal stomas. The scale was initially developed through literature research and expert consultation, and it comprised four dimensions: physiological, psychological, social, and treatment, with a total of 66 items. After item analysis, 44 items were retained. We collected scale data from 382 patients to examine its validity and reliability. The results showed that the PROS-BCAS scale had good content validity (S-CVI/Ave = 0.992), construct validity (KMO > 0.6), and discriminant validity (correlation coefficient 0.404–0.870). The Cronbach's alpha coefficients (0.801–0.954), test–retest reliability (0.778–0.956), and split-half reliability (0.896–0.977) all demonstrated good internal consistency for each dimension and the overall scale. The study demonstrated that the PROS-BCAS scale is a reliable and valid tool for accurately assessing the health-related quality of life of bladder cancer patients with abdominal stomas, providing reference for developing individualized clinical care plans.