The present study highlights the beneficial effects of premixing of highly loaded poly (butylene succinate) (PBS) / nanofibrillated cellulose (NFC) nanocomposites under solution conditions and its use as a masterbatch for melt blending. The proposed masterbatch process strategy is a very promising manufacturing technique for nanocomposites. Herein, we show the preparation of masterbatch with NFC with a very high loading of 50 wt.%. Research is aimed towards understanding the solution and melt processing effects on the structure and exploitation properties. The composites with NFC loadings from 5 up to 15 wt.% have been prepared by diluting the masterbatch and compared to conventional solvent casting. The masterbatch process significantly reduced overall solvent usage and improved the NFC dispersion within the polymer matrix. The samples prepared by solution casting showed excellent mechanical performance with an increase in elastic modulus up to 1.6-fold and storage modulus up to 2-fold at room temperature (20 °C) compared to the neat PBS, while masterbatch processed samples showed even higher overall mechanical properties – 1.8-fold and 2.5-fold increase in elastic modulus and storage modulus, correspondingly. Scanning electron microscopy (SEM) imaging indicated a homogeneous NFC dispersion for masterbatch samples and revealed agglomeration of NFC for the solvent cast ones. Biodegradation studies in the composting conditions were performed to underpin the weight, visual changes, calorimetric properties, while chemical changes were studied using spectroscopy. The NFC significantly accelerated the nanocomposites' biodegradation process from 80 days for the neat PBS to 60 days for the nanocomposites. The calorimetric studies indicate that NFC promoted crystalline phase formation and reduced crystallinity, but thermal stability was not significantly affected. In addition, the reinforcement factor analysis shows that the suitable masterbatch NFC nanocomposite preparation method's choice has a high potential to obtain high-performance materials for PBS films and packaging applications.