Crustal structure controls geothermal heat flux which is a key basal boundary conditions for ice-sheet flow in Antarctica. The crustal thickness of Antarctica is well resolved at large-scale, but the smaller-scale structures and density variations in the crust remain poorly constrained. Using 3D gravity inversion constrained by seismic Moho estimates, we model crustal structure in Antarctica, resolving sedimentary basin thickness and density, crustal density and internal layering, and the Moho. Spatial variations in upper crustal density are mapped to radiogenic heat production using a petrophysically-defined mapping approach. Significant variations are observed averaging 1.2 to 1.6 µW/m3, and as high as 2 µW/m3 in West Antarctica. The crustal contribution to geothermal heat flow is similarly variable averaging 18 to 27 mW/m2 and could be up to 60 mW/m2. The mapped variations are significant for correctly representing heat flow in Antarctica.