Bladder cancer is one of the most common malignancies of urinary tract. The current study aimed to investigate the role of insulin-like growth factor II messenger RNA binding protein 3 (IMP3) expression in the prognostic evaluation of non-muscle- invasive urothelial carcinoma of the bladder.Immunohistochemistry (IHC) was carried out to examine IMP3 protein expression in specimens from 183 cases of non-muscle-invasive urothelial carcinoma, 20 cases of muscle-invasive urothelial carcinoma and 20 benign tissues adjacent to cancer tissue.The expression of IMP3 was not detected in the adjacent benign tissues. The expression intensity of IMP3 in muscle-invasive samples was significantly higher than that in non-muscle-invasive urothelial carcinoma specimens (P = .008). IMP3 expression was significantly related with advanced tumor stage (P < .001), advanced tumor grade (P = .004), and tumor recurrence (P < .001) in non-muscle-invasive urothelial carcinomas. Kaplan-Meier analysis showed that IMP3-positive patients had much lower disease-free (P < .001), progression-free (P = .002) and metastasis-free (P = .019) survival rates compared with those with IMP3-negative tumors. By multivariable Cox analysis, we also found that IMP3 expression in non-muscle- invasive urothelial carcinomas proved to be an independent unfavorable prognostic factor of disease-free survival (HR: 2.52; 95% CI, 1.39-4.56; P = .002), progression- free survival (HR: 5.19; 95% CI, 1.54-17.46; P = .008) and metastasis-free survival (HR: 4.87; 95% CI, 1.08-22.02; P = .040).Our results demonstrate that the expression of IMP3 in non-muscle- invasive bladder cancer can serve as an independent predictor that will help recognize the subgroup of patients with a high ability to relapse, progress, and metastasize and who might get the maximum benefit from an early and more aggressive treatment strategy.