Inhibition of MBNL1‐AS1 promoted the tumorigenesis of BC cells through the regulation of miR‐135a/PHLPP2/FOXO1 in vivo. The nude mice were injected with 5673 and T24 cells stably transfected with shMBNL1‐AS1, respectively. After 19 days, mice were sacrificed. A, The tumor xenografts were collected. B, Tumor size was measured every 3 days. C, The isolated tumor was weighed at day 19. D and E, qRT‐PCR analysis of relative expression of MBNL1‐AS1 and miR‐135a. F, The immunopositive materials of Ki67 were detected using immunohistochemistry staining. G, The protein levels of cell proliferative regulators (p21, p27, and cyclin D1) and apoptotic regulators (cleaved caspase‐3 and cleaved caspase‐9) were tested by western blot. H, The protein levels of PHLPP2, FOXO1, p‐AKT, and AKT were detected using western blot. **P < .01, ***P < .001. BC, bladder cancer; MBNL1‐AS1, muscleblind‐like 1 antisense RNA 1; qRT‐PCR, quantitative real‐time PCR