Brain and behavioral asymmetries (termed "lateralization"; e.g., preferential eye‐use) have been mostly described in controlled laboratory conditions, although striking similarities of hemispheric brain control for specific behaviors have also been shown in the wild. Visual lateralization may provide ecological advantages by allowing complementary roles played by the left–right lateral and frontal visual field in distant or close motion detection of predators or other threats. In this study, we tested for lateralization in aggressive behavior in wild king penguins (Aptenodytes patagonicus), seabirds breeding in a context of strong colonial aggressiveness, and subject to on‐land‐based predation of their egg or chick. We show that males initiated more agonistic interactions when a congener was located in their right frontal visual field and in their left lateral visual field. The results obtained in females were the exact opposite for each subdivision of their visual fields. Complementary lateralization in male and female penguins may be part of a more general phenomenon, allowing partners to coordinate their behavior during reproduction. This may be especially true during the period of courtship, during which these seasonally monogamous and monomorphic seabirds engage in mutual mate choice based on a complex and ritualized display of ornaments located on the left and right lateral sides of the head. Those results open exciting questions as to whether hemispheric control of aggression is a commonly selected phenotypic trait across colonial seabirds.