Cinnamaldehyde (CNA), a pungent compound in cinnamon or dried bark of cassia, is a TRPA1 agonist. The effect of 0.1-1.0% CNA on pair-fed mice with high fat and high sucrose (HFS) diet for 1 mo was investigated. The total food intake was similar in the mice fed control and CNA diets, but the body weight showed a tendency to be lower in CNA-fed mice than in control mice. By adding CNA at 0.1, 0.5, and 1.0% concentrations, the weight of the mesenteric adipose tissue decreased significantly, and there was a tendency foward lower perirenal and epididymal adipose tissue weights compared to the control. No differences were found in any blood component measured. UCP1 protein levels in the interscapular brown adipose tissue were higher in the 0.5 and 1.0% CNA groups than in the HSF group, as shown by Western blotting. Collectively, these data show that the addition of CNA diminishes visceral fat deposition in HFS diet-fed mice, in part by stimulating interscapular brown adipose tissue.