A method to fabricate continuously tapered antireflective (AR) coatings using fused deposition modelling (FDM) is presented. The method leverages FDM's ability to fabricate spatially varying 3D structures with variable polymer fill volumes, thus producing a spatially varying effective permittivity profile. The method is validated experimentally within the Ka-band. Experimental results closely match predictions, and AR treated samples demonstrate much less transmission loss than non-AR treated samples.