Bromopropane (BP) is a halogenated alkan compound used in various industries as chemical intermediates, extraction solvents, and degreasing compounds. Halogenated alkan compounds can damage the nervous system, immune system, and hematopoietic and reproductive functions in animals and humans. However, the effect of BPs on bone formation has not yet been examined. This study examined the effects of BPs on osteoblast differentiation and analyzed the mechanisms involved in C2C12, mesenchymal stem cells. BPs dose dependently reduced the alkaline phosphatase activity, expression levels and promoter activity of bone marker genes. Additionally, 1,2-dibromopropane (1,2-DBP) significantly reduced the levels and transcriptional activity of Runx2 and Osterix, major bone transcription factors, in BMP2 induced C2C12 cells. Furthermore, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) were significantly inhibited by 1,2-DBP. These results demonstrate that BPs inhibit osteoblast differentiation by suppressing Runx2 and Osterix through the ERK/JNK pathway.