Adipogenesis is a complex sequence of events that culminates in the differentiation of fibroblast-like preadipocytes into specialized lipid-filled adipocytes and also involves a cascade of expression of many transcription factors such as peroxisome proliferator-activated receptor ${gamma}(PPAR{gamma})$ and CCAAT/enhancer-binding proteins (C/EBPs). $PPAR{gamma}$ and C/EBPs transcriptionally transactivate adipocyte specific genes, including fatty acid transport protein (FAT/CD36) and leptin. To determine whether $17{eta}$-estradiol modulates $C/EBP{alpha}$ actions on adipogenesis in high fat diet-fed female ovariectomized (OVX) C57BL/6 mice, mice were treated with $17{eta}$-estradiol for 7 days and the effects of $17{eta}$-estradiol on adipose tissue mass and expression of adipocyte specific gene as well as $C/EBP{alpha}$ were measured. Compared to vehicle-treated OVX control mice, OVX mice treated with $17{eta}$-estradiol for 7 days had lower adipose tissue weights that were similar to weights in high fat diet-fed sham-operated (Sham) mice. OVX mice showed the increased expression of $C/EBP{alpha}$ mRNA compared with Sham mice. However, $17{eta}$-estradiol treatment in OVX mice inhibited OVX induced-$C/EBP{alpha}$ activation, indicating that $17{eta}$-estradiol may act as an inhibitor of $C/EBP{alpha}$ action. Moreover, $17{eta}$-estradiol decreased mRNA levels of adipocyte marker genes, such as lipoprotein lipase, FAT/CD36 and leptin, to levels in Sham mice. These results suggest that down-regulation of adipogenesis by $17{eta}$-estradiol may be due to reduced adipose $C/EBP{alpha}$ activities in female OVX C57BL/6 mice.