Adverse experiences that occur during the early stages of life can have permanent repercussions in adulthood. Among these experiences, early weaning is one that can alter the molecular, cellular, and behavior patterns in later life. Centered on this fact, the objective of the current study was to evaluate the effect of early weaning at 15 days of life of Wistar rats on their feeding behavior and if the opioidergic system blockade would cause a reversal of these outcomes. Experimental groups were formed based on the weaning period of each litter. On postnatal day 15, the group D15 was weaned and, on postnatal day 30 (natural weaning), the group D30 was weaned. The rats weaned on postnatal day 15, and administered subcutaneous Naltrexone (3 mg/kg) were from group D15 + NTX. Those weaned at 15 days of age exhibited higher depressive-like behavior, lesser reactivity time to sucrose, and higher intake of palatable food than the control group. The Naltrexone administration was observed to reverse some outcomes, such as increasing the reactivity time to sucrose and decreasing the quantity of palatable food consumed, to levels similar to those of the control group. Together, the findings of the present study are indicative of the vital role played by the opioidergic system in inducing the changes noted in the eating behavior patterns during adulthood, post early weaning.