Bombesin receptor subtype 3 (BRS-3) is an orphan G protein–coupled receptor. Based on the obese phenotype of male BRS-3–deficient mice, BRS-3 has been considered an attractive target for obesity treatment. Here, we developed a novel selective BRS-3 agonist (compound-A) and evaluated its antiobesity effects. Compound-A showed anorectic effects and enhanced energy expenditure in dietinduced–obese (DIO)-F344 rats. Moreover, repeated oral administration of compound-A for 7 days resulted in a significant body weight reduction in DIO-F344 rats. To investigate the underlying mechanisms of BRS-3 agonist effects, we focused on the suprachiasmatic nucleus (SCN), the main control center of circadian rhythms in the hypothalamus, also regulating sympathetic nervous system. Compound-A significantly increased the messenger RNA expression of Brs-3, c-fos, and circadian rhythm genes in SCN of DIO-F344 rats. On this basis, energy expenditure enhancement by compound-A may be due to a circadian rhythm change in central and peripheral tissues, enhancement of peripheral lipid metabolism, and stimulation of the sympathetic nervous system. According to these results, BRS-3 agonist might be a good option for obesity treatment with circadian rhythm change and increase of energy expenditure.