The development of environmentally friendly polymer-based materials with antibacterial and biodegradable properties is bringing significant benefits to the packaging industry. In the present work, green-synthesized zinc oxide microporous particles (ZnO MPs) are dispersed in the poly(3-hydroxybutyrate) (PHB) matrix using a simple casting method to prepare bioactive films with improved antibacterial and anti-biofouling properties. The resultant films display a microporous morphology with a uniform dispersion of ZnO MPs within the polymeric matrix. The incorporation of green-synthesized ZnO MPs (3% wt) into PHB films leads to potent antibacterial activity, notably under LED light, with bacterial inactivation efficiencies of 97.5% and 76.2% against Escherichia coli and Staphylococcus epidermidis, respectively, after 90 min of light irradiation. This antibacterial activity is superior to that induced by films loaded with the same amount of commercial ZnO nanoparticles. Furthermore, the potent antibacterial activity gives rise to improved anti-biofouling for prepared films, in which the biofilm formation on their surface is effectively eliminated. Notably, the ZnO MP incorporation improves the microbe adhesion, accelerating the biodegradation of developed films, with soil biodegradation rates reaching 99% in 10 weeks. The present work offers a simple and cost-effective approach to producing promising composites with prolonged shelf-life and the capability of reducing bacterial contamination for packaging industry applications.