The widespread use of the pharmaceutical compound diclofenac, its toxic effects and environmental persistence, together with its inefficient removal by conventional water/wastewater treatment processes, have led to major environmental and public health concerns. Adsorption is one of the most popular advanced techniques due to its numerous advantages, such as high removal efficiency and selectivity, as well as its economical and environmental sustainability. Three-dimensional printing makes the custom production of custom-made, complex-shaped adsorbents possible. A vat photopolymerization technique was employed in order to achieve the layer-by-layer solidification of a powdered activated carbon/photopolymer suspension into the desired shape, followed by its amine functionalization. The adsorbent was characterized by FTIR, SEM, N₂ porosimetry and contact goniometry. Batch adsorption experiments in simulated diclofenac wastewater were conducted. The final pollutant concentration was spectrophotometrically determined. The successful synthesis of the composite adsorbent was confirmed. The optimum pH value was found to be 5, while kinetic and isothermal experiments were conducted at pH=7, as it corresponds to that of the secondary treated diclofenac-containing wastewater effluents. The optimum contact time was 24h. Isothermal data revealed that the material adsorption capacity decreases with temperature. The optimum solution pH value of the adsorbent’s regeneration process was found to be alkaline. Post-printing surface functionalization by diethylenetriamine increases the adsorbent’s hydrophilicity and adsorption efficiency. Post-printing diethylenetriamine modification of the adsorbent increases its diclofenac removal efficiency by 7-fold, but it also alters its surface from hydrophobic to hydrophilic. Overall, 3D printing via photopolymerization can be successfully employed for the production of activated carbon–polymer composites as efficient reusable adsorbents for diclofenac removal from wastewater.