Abstract The internal structure of Callisto has been a long‐standing question since the Galileo mission. Previous analyses suggested a largely undifferentiated interior. We present an updated interior structure for Callisto derived from a reanalysis of Galileo’s Doppler tracking data using new signal processing techniques. We present two solutions: a ‘classic’ hydrostatic model and our favored model, which accounts for non‐hydrostatic contributions from major impact basins. The latter yields a normalized Moment of Inertia (MOI) of 0.345 ± $pm $ 0.005, lower than the canonical value. Combined with magnetic induction data, our interior modeling indicates Callisto is more differentiated than previously believed. Our results favor a ∼10–120 km thick ice shell, a ∼300 km subsurface ocean—assuming the ocean partly generates the magnetic induction response—and a large rocky core with low average density. This density indicates a chondritic composition with significant mass fraction of organics, suggesting an interior configuration similar to that of Titan.