The dispersibility of nanoparticles in polymer nanocomposites significantlyaffects the mechanical, thermal, and electrical properties of the final products. The objectiveof this study is to quantify the dispersibility of nanoparticles in polymer nanocomposites. Various amounts of graphene nanoparticles were introduced in polypropylene-basedand polylactic acid-based resins through melt compounding. They were then injectionmoldedto fabricate disc-type specimens for characterizing the rheological properties ofthe nanocomposites. To evaluate the dispersibility of the nanoparticles in the composites,the associated storage (G’) and loss (G’‘) moduli were analyzed for plotting the G’-G’‘ slopes. Furthermore, the Van Gurp-Palmen plot was employed for analyzing the increase in materialelasticity with respect to the base resins and nanoparticle compositions.