Abstract Introduction/Objective Primary clear cell carcinoma of urinary bladder (PCCCUB) is a rare and aggressive cancer variant with uncertain and debatable histogenesis. The hypotheses include origins from the urothelium, pre-existing Müllerian precursors, or mesonephric remnants. Definitive diagnosis is achieved through histology and immunohistochemistry (IHC). We present an unusual case of PCCCUB in a sexagenarian woman. Methods/Case Report Patient with history of diabetes, hypertension, and smoking presented with gross hematuria. Computed tomography urogram revealed a 2.3 x 1.2 cm enhancing mass at the base of the urinary bladder. Patient underwent transurethral resection of the bladder tumor (TURBT). Histopathology revealed features of tubulo-papillary, solid, glandular structures with hyalinized stroma. Cytologic features varied from flat, hobnail, to polygonal with abundant clear to eosinophilic cytoplasm and prominent nucleoli. Immunohistochemistry revealed strong reactivity for PAX8, CK7, ER, and racemase; focal reactivity for vimentin, napsin A, p53, CA125; and non-reactivity for PAX2, WT1, PR, GATA3, pCEA, CK20, p63, p40, CD10, RCC, BRST-2, and mammaglobin. P53 showed a wild type staining pattern and Ki-67 was 10%. Combined morphologic and IHC features confirmed PCCCUB, and in the absence of muscularis mucosal invasion, tumor was staged pT1N0. PAX8 positivity and urothelial marker negativity excluded clear cell pattern of urothelial carcinoma. IHC also excluded nephrogenic adenoma, and metastasis. The female gender, and CK 7 (+)/CK 20 (−) profile supported Müllerian origin. Restaging TURBT showed consistent results. Subsequently, anterior pelvic exenteration and bilateral pelvic lymph nodes dissection was performed revealing muscularis propria invasion upstaging to mpT2 N0. Results (if a Case Study enter NA) NA Conclusion Poor prognosis, aggressive behavior, and advanced stage at the time of diagnosis warrants accurate diagnose of PCCCUB. Ambiguous origin, limited literature, and lack of clear management guidelines merit reporting in order to enhance knowledge of this rare and intriguing entity.