Biodegradable polymers have been increasingly used for scientific and commercial applications because they are similar to some conventional thermoplastics and exhibit the ability of self-degradation. Poly(3hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanocomposites films with 1 and 2 wt% of carbon nanotubes (CNT) were prepared by solution mixing, followed by solvent evaporation. In this work, PHBV/CNT nanocomposites were submitted to biodegradation in an aqueous medium for 34 days through a respirometric system. Then, the PHBV films were analyzed by the CO2 production and mineralization as a response of a microbial attack, which was monitored by back titration during all the experiment. The films were also characterized by measuring the weight loss; crystallinity was evaluated by differential scanning calorimetry (DSC) and the surface morphology by scanning electron microscopy (SEM). By analyzing the weight loss of the films, it was observed that adding CNT increases the resistance to biodegradation process. The obtained values of CO2 production and mineralization of the samples, as well as the values of weight loss, showed that the biodegradation of PHBV/CNT nanocomposites was minor in comparison to neat PHBV. The addition of CNT in PHBV matrix influences the surface morphology, causing the presence of cavities and an increase of roughness.