This paper summarizes the recent technological development in our lab on cystoscopic optical coherence tomography (COCT) by integrating time-domain OCT (TDOCT) and spectral-domain OCT (SDOCT) with advanced MEMS-mirror technology for endoscopic laser scanning imaging. The COCT catheter can be integrated into the instrument channel of a commercial 22Fr rigid cystoscopic sheath for in vivo imaging of human bladder under the cystosocopic visual guidance; the axial/transverse resolutions of the COCT catheter are roughly 9 μm and 12μm, respectively, and 2D COCT imaging can be performed with over 110dB dynamic range at 4–8 fps. To examine the utility and potential limitations of OCT for bladder cancer diagnosis, systemic ex vivo rat bladder carcinogenesis studies were performed to follow various morphological changes induced by tumor growth and in vivo porcine study was performed to examine the feasibility of COCT for in vivo imaging. Justified by promising results of the animal studies, preliminary clinical study was conducted on patients scheduled for operating-room cystoscopy for bladder cancers. Double-blind clinical results reveal that COCT can delineate detailed bladder architectures (e.g., urothelium, lamina propria, muscularis) at high resolution and detect bladder cancers based on enhanced urothelial heterogeneity as a result of excessive growing nature of bladder cancers. The diagnostic sensitivity and specificity can be enhanced to 92% and 85%, respectively. Results also suggest that due to reduced imaging depth of COCT in cancerous lesions, staging of bladder cancers may be limited to Ta or T1 for non-outgrowing cancerous lesions.