Three-dimensional (3D) printing by Fused Deposition Modeling (FDM) offers a flexible platform for fabricating personalized medicines with tunable release profiles. However, developing printable filaments with suitable mechanical properties and controlled drug release remains challenging. Ketoprofen was formulated into FDM-printed polyvinyl alcohol (PVA) capsule shells which were subsequently filled with ketoprofen powder and locked to form complete 3D‑printed capsules, spanning immediate-, sustained-, and delayed-release designs; a dual-compartment polypill with famotidine was also produced. Capsule shell geometry and internal density were systematically varied to modulate drug release, and performance was evaluated using pharmacopeial quality tests, dissolution studies, micro-computed tomography, and in silico pharmacokinetic simulation. Capsule geometry and polymer choice modulated release: low shells/infill density accelerated immediate-release (IR) whilst higher shells/infill density prolonged sustained-release (SR). Selected IR and SR capsules achieved a similarity factor f2 ≥ 50 vs references. Micro-CT confirmed design–porosity differences; solid-state data supportedthe formation of largely amorphous solid drug–polymer dispersions in Kollicoat IR formulations and solvent evaporation products. Simulations predicted distinct IR vs SR plasma profiles. These findings illustrate that FDM printing can modulate oral drug release through geometry and, together with in silico tools, provide a framework for designing customized capsules.