JAZF1 is a 27 kDa nuclear protein containing two putative zinc finger motifs that is associated with diabetes mellitus and prostate cancer according to genomewide association studies; however, little is known about the function of this gene in regulating metabolism. Recent evidence indicates that JAZF1 transcription factors bind to the nuclear orphan receptor TR4 and act as a strong repressor. This receptor regulates PEPCK, the key enzyme in gluconeogenesis, at the transcriptional level. Excess PEPCK expression in mice causes hyperglycemia, hyperinsulinemia, and increased glucose turnover. Therefore, we hypothesized that ectopic expression of Jazf1 may lead to abnormal expression of PEPCK that allow for the metabolic disorder. To elucidate its role in metabolism, we fed the mice with high- or normal- fat diet up to 18 weeks. In the liver tissue of mice, Jazf1 overexpression led to a substantial reduction in the expression of PEPCK. In Jazf1 overexpression mice, weight gain was found to be significantly decreased and increment of blood glucose level also decreased. Our data suggest that Jazf1 plays a critical role in the regulation of energy and lipid homeostasis, and promotes the development of metabolic disorder. Jazf1 may provide a new therapeutic target in the management of obesity, diabetes, and liver steatosis.