Balancing pathogen defence with maintaining tolerance to benign antigens in the neonatal period is essential for survival and the establishment of life-long immune homeostasis. It is becoming apparent that conventional dendritic cells (cDCs) adapt their functions in response to homeostatic environmental cues, which allows them to shape age-specific immunity while maintaining immune homeostasis. We are investigating the molecular mechanisms that determine the functions of cDCs in specific tissues and across age. Our work has identified the period from birth to weaning—marked by the transition from milk to solid food—as a critical window for the age-dependent regulation of cDCs in spleen. During this time, we have uncovered a diet induced interferon (IFN)-γ-driven regulatory circuit that relays dietary cues to cDC1 in spleen. IFNγ-mediated STAT1-signaling induces an immunogenic maturation program in splenic cDC1 that instructs them to expand effector memory CD8⁺ T cells. This program emerges during weaning, occurs independent of the microbiota and remains responsive to dietary intervention in adult mice. During the transition from breastfeeding to solid food this circuit relays dietary information to splenic cDC1 to shape the effector phenotype of food-antigen specific CD8⁺ T cells in a feed-forward manner, allowing cDC1 to recalibrate the T cell pool at the moment of nutritional independence. cDC1 maturation remained responsive to dietary intervention in adult mice, highlighting the therapeutic potential of dietary intervention to modulate cDC function beyond the weaning period.