Compounds of plant origin are used in biodegradable polymers as stabilizers and functional additives. However, these substances often have a biological activity (antimicrobial) that can affect the biodegradability of these polymers. The objective of this work is to study the effect of two polyphenols, quercetin and gallic acid on the biodegradability of the natural polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The biodegradation of the materials was evaluated in pure liquid culture media in the presence of the PHBV-degrading bacterium Streptomyces exfoliatus, and also by a respirometric test in compost. The bacterial inhibition was demonstrated from the second and fourth month of incubation in the presence of quercetin and gallic acid, respectively. This was confirmed by optical microscopic observations of the bacterial cells (showing the disappearance of the bacterial filament network) and scanning electron microscopy analysis (showing no structural change on the surface of the additivated films). However, all the films produced were considered fully biodegradable, according to the specification standard NF T51-800, leading to the conclusion that the use of polyphenolic additives to PHBV materials (instead of synthetic additives) to improve their functionality is not an obstacle to their biodegradation in home compost.