Mammalian dams consume a large amount of energy for rearing their pups. Because the dams utilize energy obtained from food for themselves and their offspring's survival, the excess energy expenditure for lactation threatens a mother's survival. Here, we demonstrate that an orexigenic molecule neuropeptide Y (NPY) in the dorsal raphe nucleus (DRN) mediates fasting-induced inhibition of maternal behavior in mice. We first examined the involvement of the DRN with the expression of maternal behavior, including maintenance of the nest, retrieving behavior, and crouching behavior. When a 5-HT1A agonist, GABAA receptor antagonist, and GABAB receptor antagonist were administered into the DRN, all the treatments suppressed the expression of maternal behavior in non-fasted dams, indicating that serotonergic (5-HT) and GABAergic neurons are involved in the expression of maternal behavior. After 9-h-fasting, dams showed a dramatic decrease in the expression of maternal behavior. Intracerebroventricular or direct DRN injection of NPY inhibited the expression of maternal behavior in non-fasted dams. In contrast, injection of the NPY Y1 receptor antagonist BIBP-3226 into the DRN, in which expression of the Y1 receptor was confirmed in 5-HT and GABAergic interneurons, recovered the expression of maternal behavior in fasted dams. When the pups were presented, the increase in the number of c-Fos-positive GABAergic, but not serotonergic, neurons was smaller in fasted than in non-fasted dams. These results suggest that NPY may inhibit pup-induced activation of GABAergic neurons via the Y1 receptor. A 5-HT2A receptor agonist and a GABAB receptor agonist, but not a GABAA receptor agonist, recovered the expression of maternal behavior in fasted dams. These results suggest that NPY inhibits both 5-HT neuronal activity and its modulation via the GABAB receptor, resulting in the inhibition of maternal behavior in food-restricted dams.