The aim of this study was to evaluate the effect of human serum (HS) on growth and differentiation capacity of human synovium-derived mesenchymal stem cells (MSC) in comparison to cells grown in fetal bovine serum (FBS). Human MSCs were isolated from the synovium of knee joints of three donors and the cells were cultured individually in varying concentrations of allogenic HS or FBS. Bovine MSCs were isolated from synovium and cultured in the same manner. Cell proliferation was assessed by the tetrazolium assay after passage 3. The capacity for chondrogenic and osteogenic differentiation was investigated in specific media followed by 1,9-dimethylmethylene blue assay and alcian blue staining, or by alizarin red staining, respectively. Human MSCs proliferated significantly more rapidly in the presence of HS than with equivalent levels of FBS. Chondrogenic or osteogenic differentiation occurred to nearly identical levels in HS or FBS. The results of this study indicate that HS is superior for the culture of human MSCs compared with FBS in terms of cellular expandability, without losing chondrogenic or osteogenic differentiation capacity. Coupled with the advantage in eliminating the potential risk accompanied with the use of xeno-derived materials, pooled, well-characterized HS could be a useful reagent to promote cellular expansion for clinical synovial stem cell-based therapy.