Rectal bleeding in neonates is an alarming sign that suggests a possible serious underlying condition, such as infection or bleeding disorder that would necessitate hospitalization and prompt intervention. We report a case of eosinophilic gastroenteritis caused by cow's milk protein allergy in a oneday-old infant, who presented with frankly bloody stools associated with massive gastrointestinal and peripheral blood eosinophilia prior to initiation of enteral feedings. The patient's outcome was favorable, with complete spontaneous recovery in one week, after a period of bowel rest, parenteral nutrition, and use of amino acid formula. The eosinophilia was also transient and gradually resolving by two months of age. Rectal bleeding secondary to allergic colitis caused by cow's milk sensitization may occur in neonates, and failure to appreciate this possibility may lead to inappropriate diagnostic or therapeutic intervention.