Different amounts of graphene nanoplatelets (GNPs) were embedded in two different biodegradable polymers: poly lactide (PLA) and poly (butylene adipate-co-terephthalate) (PBAT). Variations of the physical properties of these two systems with GNP loading were investigated via different techniques. Morphology of the nanocomposites was studied via scanning electron microscopy and X-Ray diffraction. Thermal properties and thermal stability of the nanocomposites were determined from differential scanning calorimetry and thermogravimetric analysis, respectively. The glass and melting temperatures of the matrices did not vary considerably with GNP incorporation but their crystallinity was affected. Crystallinity of PBAT decreased slightly with increasing GNPs while that of PLA increased markedly. Thermal stabilities of both polymers were effectively improved. In particular, degradation of PLA was significantly reduced due to the presence of GNPs. Dielectric properties over X-band frequency range and DC electrical conductivity of the nanocomposites were also determined. Conductivity of both polymers increased with increasing GNP concentration and both systems demonstrated a percolation of between 6 and 9 wt% GNPs. PLA nanocomposites with 9-15 wt% GNPs exhibited significantly higher conductivity values than those of PBAT nanocomposites. It was also observed that while dielectric constants of both systems had comparable values for the same GNP contents, PLA nanocomposites had higher values of dielectric loss than PBAT nanocomposites for filler loadings of 9-15 wt%. In conclusion, results showed a general trend of enhancement in the properties of the two matrices with GNP addition. However, effect of GNP embedding was more pronounced on PLA's physical properties compared to PBAT.