ABSTRACTThis study describes the occurrence of hyperostosis, to the best of our knowledge, for the first time in Trachinotus marginatus Cuvier 1832 and examines its patterns in 21 specimens from Rio de Janeiro, Brazil. Radiographic images revealed the presence of the condition in 76.2% of the individuals, affecting five distinct bone regions: supraoccipital (76.2%), dorsal‐fin pterygiophore (52.3%), anal‐fin pterygiophore (9.5%), rib (4.8%) and hemal spine (4.8%). Hyperostosis was consistently observed in the first dorsal pterygiophore and was not found in the other dorsal pterygiophores. A directional linearity was noted in the growth of the supraoccipital crest in the cranial region as the sexual maturation of individuals progressed, demonstrating a tendency for bone expansion. Although hyperostosis is a species‐specific condition, the studied species did not exhibit a clear relationship between specific bone region patterns and the total length of the individual, suggesting no progression in the same affected regions as the animal grows. Longitudinal histological sections of the supraoccipital and ribs revealed high bone porosity caused by hyperostosis, with the presence of several vascular channels. This study represents the first report of the condition of this species, which is an important resource for artisanal fishing in southern Brazilian waters.