Throughout an animal’s life, species may occupy different environments and exhibit distinct life stages, known as ontogenetic shifts. Life histories of most cartilaginous fishes are characterized by these ontogenetic shifts, defined by changes in habitat and diet, as well as behavioral changes at the onset of sexual maturity. In addition, cartilaginous fishes experience indeterminate growth, whereby both the brain and body grow continually throughout their lives. Despite lifelong neurogenesis in these species, little work has been done on ontogenetic changes in brain size or brain organization, which may be informative about functional shifts in sensory and behavioral specializations. This study quantified ontogenetic changes in brain-body scaling and the scaling of seven major brain regions in 35 specimens of the Atlantic sharpnose shark, Rhizoprionodon terraenovae, at all stages of maturity. Relative brain size increased significantly with body mass throughout ontogeny in this species, and the telencephalon, diencephalon, optic tectum, and medulla oblonga scaled with negative allometry against brain mass. However, notably, the olfactory bulbs and cerebellum scaled hyperallometrically to the rest of the brain, whereby these structures enlarged disproportionately as this species matured. Changes in the relative size of the olfactory bulbs throughout ontogeny may reflect an increased reliance on olfaction at later life history stages, while changes in the relative size of the cerebellum throughout ontogeny may be indicative of the ability to capture faster prey or an increase in migratory behavior as this species moves to offshore habitats, associated with the onset of sexual maturity.