Sustainable polymers from renewable resources are classified as biobased polymers. Poly(lactic acid) (PLA) is one of the most common biobased polymers applied in the biodegradable plastic industry as a feasible substitute of petrochemical-derived products. Cardanol oil (CA), a renewable resource and relatively low-cost side product of the cashew agro-industry, combined with neat PLA permitted the preparation of plasticized PLA/CA films by means of hot melt extrusion processes. Looking at packaging applications of the functional biobased PLA/CA films, chemical, mechanical, thermal, antioxidant, and barrier properties were studied. Thermal analysis revealed that the PLA glass-transition temperature decreased with the increasing content of CA, indicating that CA worked as a plasticizer for PLA. The presence of CA increased the oxygen transmission through the PLA/CA films; consequently, the permeability values were always appreciably higher for plasticized films. Nevertheless, the CA-plasticized PLA films showed good barrier properties similar to packaging materials commonly used in the food industry today. Release studies from PLA/CA films were carried out in four food simulants (physiological saline solution, ethanol, acetic acid, and isooctane) through spectrophotometric measurements and revealed the release effects only in simulants for fatty foods. Radical scavenging assays indicated the elevated antioxidant activity of CA-incorporated films compared to neat PLA.