Although GATA binding protein 3, a zinc finger transcription factor and an estrogen receptor-regulated gene, has recently been suggested as a marker for urothelium, prognostic significance of GATA binding protein 3 expression in bladder tumor remains unclear. We immunohistochemically stained for GATA binding protein 3 in urothelial neoplasm and matched nonneoplastic bladder tissue specimens. GATA binding protein 3 was positive in 125 (86%; 13 [9%] weak, 44 [30%] moderate, and 68 [47%] strong) of 145 bladder tumors, which was significantly lower than in benign urothelium (104/106 [98%]; 3 [3%] weak, 30 [28%] moderate, and 71 [67%] strong) (P=.001). Fifty (98%) of 51 low-grade tumors were GATA binding protein 3 positive, whereas 75 (80%) of 94 high-grade carcinomas were GATA binding protein 3 positive (P=.002). Similarly, 78 (98%) of 80 non-muscle-invasive tumors expressed the GATA binding protein 3, compared with 47 (72%) of 65 muscle-invasive tumors (P<.001). Conversely, among 68 cases treated with cystectomy, significantly lower expression of GATA binding protein 3 was found in pN0 tumors (32/47 [68%]) than in node-positive tumors (20/21 [95%]) (P=.027). Kaplan-Meier and log-rank tests further revealed that overall positivity (P=.048) or strong positivity (P=.025) of GATA binding protein 3 correlated with progression of muscle-invasive tumors. Multivariate analysis identified high GATA binding protein 3 expression as a strong prognosticator for progression (P=.052) and cancer-specific survival (P=.040) of muscle-invasive tumors. Moreover, there were significant correlations between GATA binding protein 3 expression vs androgen receptor overexpression, estrogen receptor α overexpression, or loss of estrogen receptor β expression. Thus, compared with benign urothelium, a significant decrease in the expression of GATA binding protein 3 in urothelial neoplasms was seen. Loss of GATA binding protein 3 was associated with high-grade and/or muscle-invasive tumors, whereas strong expression was an independent predictor of poor prognosis.