Tonicity-responsive binding protein (TonEBP) is a widely expressed transcription factor whose activity is regulated by extracellular tonicity. Recent studies have reported tonicity-dependent interaction between TonEBP and p65 subunit of NF-κB which results in an increase of NF-κB activity. Because NF-κB plays an important role in the obesity-induced metabolic inflammation and leptin resistance, TonEBP may also be involved in the metabolic diseases. In the beginning of this study, we found that TonEBP expression was increased in the hypothalamus of mice by feeding high-fat diet (HFD). Mice with heterozygous TonEBP deficiency [TonEBP (+/-)] revealed higher sensitivity to leptin compared to wild type littermate. When fed HFD, TonEBP (+/-) mice were significantly less obese and showed an alleviated leptin resistance, compared to the wild type. Because suppressor of cytokine signaling 3 (SOCS3) is a negative regulator of leptin signaling, we next addressed change in SOCS3 expression by TonEBP. Leptin-induced SOCS3 expression was significantly decreased in the hypothalamus of TonEBP (+/-) mice. Moreover, our promoter analysis revealed that NF-κB-TonEBP complex markedly stimulated transcriptional activity of SOCS3. These results suggest that TonEBP is involved in the leptin signaling pathway through controlling SOCS3 expression in the hypothalamus, and thereby plays an important role in generation of metabolic disorder