Aseptic loosening induced by wear debris particles of artificial joint is characterized by a considerable suppression of osteogenesis. The objective of this investigation was to determine the effect of different-sized titanium particle on protein synthesis, and mineralization in bone marrow–derived mesenchymal stem cells(BMSCs) induced toward osteogenic differentiation in vitro. Rat bone marrow–derived mesenchymal stem cells (rBMSCs) induced toward osteogenesis were cultured in the presence or absence of titanium particles in varied size, 0.9µm, 2.7µm, 6.9µm, respectively. Flow cytometry characterization of rBMSCs proved 99% homogeneity by using with cell-surface antibody. The bone matrix protein synthesis evaluation showed that three size groups of titanium particles could suppress early, middle, and late markers of the osteogenic lineage, i.e., alkaline phosphatase activity, C-terminal type I procollagen and osteocalcin secretion repectively, in a dose- and time-dependent manner. The least detrimental particle size group was 0.9 μm, which is a reasonable finding as this group is more susceptible to phagocytosis due to smaller size. The cell-mediated matrix mineralization in terminally differentiated cultures by Alizarin Red S assay revealed a reduction in the number and area of mineralizing nodules, even mineralization calcium concentration in BMSCs cultures after titanium particles treatment. Collectively, the data suggest that different size titanium particles alters osteogenic differentiation in BMSCs cultures during lineage progression and provide further insight into wear debris-induced reduced bone formation.