Mori Cortex (MC), the root bark of the mulberry tree (Morus alba L.), has been used traditionally in several Asian countries for medicinal purposes due to its anti-inflammatory, hypoglycemic, and antibacterial activities, as well as its antiviral effects. In the present study, we found that ethanolic extract of Morus alba L. root bark (MC) accelerated differentiation of 3T3-L1 preadipocyte cells. Treatment with MC resulted in enhanced triglyceride (TG) accumulation and increased mRNA levels of C/$EBP{alpha}$ (CCAAT/enhancer-binding protein ${alpha}$) and $PPAR{gamma}$ (peroxisome proliferator-activated receptors ${gamma}$); however, their upstream regulator, C/$EBP{delta}$, showed a dose-dependent decrease during adipocyte differentiation. Immunoblot analysis indicated that MC induced an increase in expression of adipogenic maker proteins, such as $PPAR{gamma}$, adipocyte-specific fatty acid binding protein 4 (aP2), and GLUT4 (glucose transporter 4). Results of the reporter gene assay revealed that MC did not show $PPAR{gamma}$ ligand activity even at a high dose (50 ${mu}g/mL$), suggesting that enhanced expression of $PPAR{gamma}$ resulted not from $PPAR{gamma}$ ligand activity but by other mechanisms that might be related to the $PPAR{gamma}$ signal pathway. In conclusion, our findings suggest the potential for use of MC as a possible therapeutic material for treatment of dyslipidemia and type 2 diabetes by increasing $PPAR{gamma}$ transcriptional activities.