In this study, we aimed to compare how the microstructure and architecture of polymer supports influence adhesion, growth and differentiation of human mesenchymal stem cells (hMSC) in the context of bone tissue engineering. We manufactured poly(L-lactide-co-glycolide) (PLGA) three-dimensional supports in the form of microspheres by emulsification and porous scaffolds by solvent casting/porogen leaching. HMSC were seeded on both materials and on control tissue culture polystyrene (TCPS, bottom of the wells) and cultured in basal or osteogenic medium for 1, 3, 7 and 14 days. HMSC proliferation and osteogenic differentiation were studied using lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) assays, respectively. Furthermore, cell morphology and viability were analyzed after live/dead fluorescence staining. The results show that the optimized emulsification conditions allowed the production of PLGA microspheres with a median size of 95 µm. The PLGA scaffolds had a porosity of 82.1% ± 4.2% and a pore size of 360 µm ± 74 µm. HMSC cultured on control TCPS in osteogenic medium were more spread and polygonal than those in basal medium. They were characterized with a lower proliferation rate, as shown by the LDH results, but higher ALP activity. This suggests that hMSC osteogenic differentiation was achieved. The same tendency was observed for cells cultured on microspheres and scaffolds. Cell proliferation was more efficient on both materials and control in growth medium as compared to differentiation medium. The amount of ALP, i.e. a marker of osteogenic differentiation, was elevated, as expected, in differentiation medium. However, on day 14 cells cultured on the scaffolds in basal medium exhibited the same osteogenic potential as those cultured in differentiation medium. In general, both microspheres and scaffolds promoted hMSC adhesion, proliferation, and osteogenic differentiation and may be used for bone tissue engineering.