Treatment of epilepsy or bipolar disorder with valproic acid (VPA) induces weight gain and increased serum levels for the satiety hormone, leptin, through an unidentified mechanism. In this study we tested the effects of VPA, a short-chain branched fatty acid (C8:0), on leptin biology and fatty acid metabolism in 3T3-L1 adipocytes. VPA significantly reduced leptin secretion in a dose dependent manner. Since fatty acid accumulation has been hypothesized to block leptin secretion, we tested the effect of VPA on fatty acid metabolism. Using ¹⁴C-radiolabeled VPA, we found that the ¹⁴C was mainly incorporated into triacylglycerol (TAG). VPA did not alter lipogenesis from acetate, nor did it change the amount of intracellular free fatty acids available for TAG synthesis. Decreased leptin secretion was accompanied by a reduction in leptin mRNA, even though VPA treatment did not alter the protein levels for known transcription factors affecting leptin transcription including: CCAAT/enhancer binding protein , peroxisome proliferator-activated receptor , or steroid regulatory element binding protein 1a. VPA altered levels of leptin mRNA independent of de novo protein synthesis without affecting leptin mRNA degradation. This report demonstrates that VPA decreases leptin secretion and mRNA levels in adipocytes in vitro, suggesting that VPA therapy may be associated with altered leptin homeostasis contributing to weight gain in vivo.