Overactivity of the hypothalamic–pituitary–adrenal (HPA) axis has been linked to affective disorders such as anxiety and depression. Dampening HPA activity has, therefore, been considered as a possible means of treating affective disorders. Given the important role of vasopressin in modulating the HPA axis, one strategy has focused on inhibiting activity of the vasopressin 1b (V_1b) receptor. In animals, V_1b receptor antagonists reduce plasma stress hormone levels and have been shown to have an anxiolytic-like effect. Recently, V1B-30N was identified as a highly potent V_1b receptor antagonist with selectivity over other vasopressin receptors, which is evaluated here in rodent models of anxiety-like and depression-like behaviors. V1B-30N (1–30 mg/kg, IP) dose-dependently reduced separation-induced vocalizations in rat pups without producing any sedative effects in the animals. Similarly, V1B-30N (3–30 mg/kg, IP) dose-dependently reduced separation-induced vocalizations in guinea pig pups. In a conflict assay, conditioned lick suppression, V1B-30N (3–30 mg/kg, IP) increased punished licking. To assess antidepressive-like properties, V1B-30N (1–30 mg/kg) was tested in the mouse and rat forced-swim tests but was found to be inactive. These results are consistent with previous findings with other V_1b antagonists, which suggest that acute pharmacological antagonism of the V_1b receptor has anxiolytic-like but not antidepressant-like properties.