Diosmin is a compound that is widely distributed in citrus. The aim of this study was to examine the effects of diosmin on osteoblast differentiation using MC3T3-E1 preosteoblast cells. The effect of diosmin on mRNA expression levels of osteogenic genes in MC3T3E1 cells were determined by RT-PCR. Diosmin regulated expression of key osteogenic genes such as dNA-binding protein inhibitor (Id1), runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), and osteocalcin (OC) during osteoblast differentiation, and promoted recovery of tumor necrosis factor (TNF)-α-reduced osteogenesis. Alizarin Red S staining was performed to evaluate mineralization. Diosmin enhanced mineralization and recovery of TNF-α-reduced osteoblast differentiation. These results suggest that diosmin may enhance osteoblast differentiation and recovery of TNF-α-reduced osteoblast differentiation, and it may be a candidate for treating osteoporosis.