Biodegradable polymers such as poly(butylene adipate-coterephthalate)(PBAT) have attracted great interest as alternatives to traditional petroleum-based polymers. Nonetheless, it is necessary to improve some properties of PBAT, such as mechanical strength. Cellulose nanofiber(CNF) can improve PBAT mechanical strength, but its dispersion and compatibility in the PBAT matrix require further improvement. In this study, octadecylamine(ODA) was utilized to graft-modify CNF to change the fiberto-fiber interaction and improve its compatibility with the PBAT matrix.PBAT composites with 1 wt% CNF were prepared using a masterbatch premixing method to avoid CNF aggregation during extrusion. The effects of ODA graft modification on CNF properties were studied; varying degrees of CNF modification were investigated for their effect on PBAT properties. ODA-modified CNF(OCNF)/PBAT melt-extruded composites possessing17.2% higher tensile strength than pure PBAT polymer were obtained without affecting the thermal stability of PBAT. As a result, surface modification of CNF with ODA is an effective strategy for improving CNF-PBAT compatibility.