To avoid disturbing membrane functioning while preventing biofilm formation, antibacterial agents were incorporated in membrane spacers that are currently inert elements in the membrane processes. 3D-printed PA11 membrane spacers with different wt. % of magnesium oxide (MgO) were shaped and characterized Several extrusions allowed to increase the percentage of MgO incorporated up to 10 wt. %. Scanning electron microscope equipped with Energy-dispersive X-ray confirmed the presence of MgO and showed the morphology and distribution of those particles. Thermo-mechanical properties were evaluated using dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, and mechanical assays. No significant difference, in melting and glass transition as well as tensile properties, was found due to the addition of MgO, except a slight decrease in degradation temperature. The addition of MgO decreased the water contact angle of the materials. Biological assays against E. coli and S. aureus showed that increasing MgO wt. % up to 7.5 lead to a significant decrease in bacterial colonization of both strains. This study points out the potential of a simple and efficient way to provide antibacterial properties to membrane spacers to overcome biofouling in wastewater treatment applications.