In this study, the osteogenic potential of rat bone marrow mesenchymal stem cells (rBM-MSCs) on a biomimetic poly(ε-caprolactone)/β-tricalcium phosphate (PCL/β-TCP) composite scaffold composed of parallel concentric fibrous membranes was evaluated in vitro and in vivo. PCL/β-TCP composite membranes were prepared by electrospinning and characterized by x-ray diffraction, differential scanning calorimetry, Fourier transform-infrared spectroscopy, and scanning electron microscopy (SEM). rBM-MSCs were seeded on three-dimensional multispiral scaffolds prepared by the assembly of composite membranes. The cell-scaffold constructs were cultured in osteogenic medium for 4 weeks. Histochemical studies and biochemical assays confirmed the osteogenic differentiation of rBM-MSCs inside the scaffold by documenting the dense mineralized extracellular matrix formation starting from the second week of culture. In the in vivo part of the study, cell-scaffold constructs precultured for 7 days were implanted subcutaneously into the epigastric groin fascia of Wistar rats for a duration of 6 months. Ectopic bone-tissue like formation was documented by using computerized tomography, confocal laser microscopy, SEM, and histochemistry. In vivo findings indicated that the biomimetic multispiral scaffold seeded with rBM-MSCs supports the ectopic formation of new bone tissue in Wistar rats.