Human and mouse urocortin 3 (Ucn3) were first identified in 2001. Ucn3 binds selectively to corticotropin-releasing factor receptor type 2 (CRF-R2). Previous studies have shown that centrally administered Ucn3 decreases food intake in rats. However, the role of Ucn3 in the regulation of gut motility remains to be determined. In the present study, we investigated the effects of peripherally administered Ucn3 on food intake and gastric emptying in mice. After intraperitoneal (i.p.) administration of Ucn3, food intake was measured in the light and dark phases, and the rate of gastric emptying was determined. We found that i.p. administration of Ucn3 significantly inhibited feeding behavior in mice, and significantly delayed gastric emptying 1-2 h after administration in a dose-dependent manner. These results suggest that Ucn3 contributes to the modulation of feeding behavior and gut motility. Thus, Ucn3 and CRF-R2 may be involved in the pathogenesis of functional gastrointestinal and eating disorders.