The nuclear receptor corepressor (NCoR) regulates the activities of gene transcription. Mesenchymal stem cells (MSCs) derived from bone marrow are multipotent cells which can differentiate into osteoblasts and adipocytes. This study was conducted to investigate the effects of NCoR on adipogenic differentiation of MSCs isolated from the rats. The results suggested that rat MSCs could differentiate into adipocytes successfully after cultured in adipogenic medium. NCoR protein determined by Western blot showed a lower expression in MSC-derived adipocytes, indicating that NCoR was involved in adipocyte differentiation of rat MSCs. It further proved that small interfering RNA (siRNA)-mediated knockdown of NCoR could promote cell viability and differentiation and enhance messenger RNA (mRNA) expression of lipoprotein lipase (LPL) and protein expression of CCAAT/enhancer binding protein-α (C/EBPα) and peroxisome proliferator-activated receptor-γ (PPARγ). However, over-expression of NCoR exerted its functions in contrary to NCoR knockdown. It indicated that NCoR could negatively regulate adipogenic differentiation of rat MSCs.