King penguins (Aptenodytes patagonicus) are colonial seabirds presenting an extraordinary breeding cycle. Parents take over 14 months to raise a single chick to independence, upon which fledglings depart at sea for more than a year. Juveniles often return to the colony within the three austral summers following departure, and before the age of first reproduction (around 5-6 years old), possibly to acquire the essential skills involved in breeding. Little to nothing is known on the acquisition of parental behaviour. Here, we report an anecdotal, yet highly unusual, observation of chick-chick feeding behaviour in this species. The behaviour is highly unusual in that two non-sibling chicks, not yet independent, and hatched at different times (early and late) of the same breeding season were observed, the older chick feeding the younger one. Whereas alloparental feeding is known to occur in this species, this is the first reported observation of a chick-chick feeding event. This unusual behaviour raises the question of whether the early social environment plays a role in the acquisition of essential parenting skills in this species. © 2023 Anne Cillard et al.