Pinellia ternata is known as the herb effective in removing dampness-phlegm, one of the causes of obesity in traditional Korean medicine. Pinellia ternata water extract (PE) was fed to rats after mixing with diet once a day (400 mg·kg⁻¹) for 6 weeks. We investigated its effect on the thermogenesis and fatty acids oxidation with obese Zucker rats. We also determined the gene expression of uncoupling protein 1 (UCP1), peroxisome proliferators-activated receptor α (PPARα), and PPARγ coactivator 1α (PGC1α). The PE treatment lowered the levels of triglyceride and free fatty acids (p<0.05) in blood of the obese rats and the body weight was also reduced slightly. It was also observed that PE significantly increased the expression of both UCP1 mRNA in brown adipose tissue (BAT) (p<0.001) and PPARα and PGC1α mRNA in white visceral adipose tissue (WAT) (p<0.05 and p<0.001, respectively), which may cause a reduction of obesity. These results suggested that PE would be able to affect anti-obesity through thermogenesis and fatty acid oxidation.