The object of this study was to investigate the role of scaffold porosity on tissue ingrowth using hybrid scaffolds consisting of bladder acellular matrix and electrospun poly (lactide-co-glycolide) (PLGA) microfibers that mimic the morphological characteristics of the bladder wall in vitro and in vivo. We compared single-spun (SS) PLGA scaffolds with more porous cospun (CS) scaffolds (PLGA and polyethylene glycol). Scaffolds were characterized by scanning electron microscopy. Bladder smooth muscle cells (SMCs) were seeded, and proliferation and histological assays were performed. Sixteen rats were subjected to augmentation cystoplasty with seeded SS or CS scaffolds, morphological, and histological studies were performed 2 and 4 weeks after implantation. The porosities of SS and CS scaffolds were 73.1 ± 2.9% and 80.9 ± 1.5%, respectively. The in vitro evaluation revealed significantly deeper cell migration into CS scaffolds. The in vivo evaluation showed significant shrinkage of SS scaffolds (p = 0.019). The histological analysis revealed a bladder wall-like structure with urothelial lining and SMC infiltration in both groups. The microvessel density was significantly increased in the CS scaffolds (p < 0.001). Increasing the porosity of electrospun hybrid scaffolds is an effective strategy to enhance cell proliferation and distribution in vitro and tissue ingrowth in vivo.