© 2018, Springer Nature Switzerland AG. Siblings often compete for limited resources, particularly food provided by their parents. Such competition is usually nonviolent, but direct aggression has evolved in some species. However, there is little knowledge about sibling aggression in species without parental provisioning. Here, we investigated sibling aggression in the cichlid Neolamprologus furcifer in Lake Tanganyika, Zambia. In this species, females guard their broods in the nest but do not provide any food. Early-stage fry did not show any sibling aggression while foraging on plankton, but began to show nonlethal aggression once they started to forage on small benthic shrimp at 2 weeks of age. The frequency of sibling aggression decreased at week 7, when the density of fry decreased remarkably. Sibling aggression also decreased following a short-term increase in food through supplemental feeding. The aggression was higher in the morning than in the afternoon despite higher abundance of shrimp at that time, and decreased when the number of shrimp in the nest was experimentally reduced. These results indicate that food availability affects sibling aggression of animals that do