Pleiotrophin (PTN) plays diverse roles in cell growth and differentiation. In this investigation, we demonstrate that PTN plays a negative role in adipogensis and that glycogen synthase kinase 3β (GSK‐3β) and β‐catenin are involved in the regulation of PTN‐mediated preadipocyte differentiation. Knocking down the expression of PTN using siRNA resulted in an increase in phospho‐GSK‐3β expression, and the accumulation of nuclear β‐catenin, which are critical downstream signaling proteins for both the PTN and Wnt signaling pathways. Our investigation suggests that there is a PTN/PI3K/AKT/GSK‐3β/β‐catenin signaling pathway, which cross‐talks with the Wnt/Fz/GSK‐3β/β‐catenin pathway and negatively regulates adipogenesis.