AbstractPrevious studies have reported antioxidant and antimicrobial activity of guabiroba extract (GE), which is associated to its polyphenolic and carotenoid contents. Encapsulation using polymeric materials could improve GE application, bioavailability, and stability in foods and pharmaceuticals. Poly (dl-lactide-co-glycolide) (PLGA) nanoparticles with entrapped GE were synthesized using the emulsion-evaporation method with different lactide to glycolide (50:50 and 65:35) ratios to determine the dependency of polymer composition on nanoparticles antioxidant and antimicrobial activities. Controlled release experiments showed an initial burst followed by a slower release rate of carotenoids inside PLGA matrix. Both nanoparticles showed Listeria innocua growth inhibition within the concentration range tested (<1200 μg/mL), that was not observed by the free extract. Lower GE concentrations were required to reduce reactive oxygen species once it was nanoencapsulated; however, equivalent or higher concentrations for free radical scavenging were required. GE-loaded PLGA 50:50 presented the best results for antimicrobial and antioxidant delivery applications. These nanoparticles could be used with other extracts containing carotenoids and other functional lipids as delivery systems for enhanced biological activity.