Growth hormone (GH) has an inhibitory effect on adipogenesis, and its effect is associated with insulin action in obesity. In this study, the relationship between GH effect on insulin sensitivity and adipocyte differentiation in vivo was investigated. Transgenic (TG) female mice expressing porcine GH had reduced body weights and weights of retroperitoneal and parametrial fat depots. Insulin treatment increased PPARγ and GLUT4 expression in adipose tissue of WT mice but had no effect in TG mice. Content of transcription factors, PPARγ and C/EBPα and β, was higher in adipose tissue of WT mice, and for C/EBPα and PPARγ, the difference occurred primarily in 24-, compared to 12-week-old, mice. Expression of preadipocyte factor-1 was higher in adipose tissue of TG mice, and expression of TNF-α and leptin was reduced in adipose tissue of 24-week-old TG mice. Our results suggest that increased expression of GH reduces adipogenesis by inducing adipocyte resistance to the adipogenic effect of insulin.