AbstractInterfacial compatibility plays a key role in the performances of natural fiber-reinforced composites. The measures commonly used to improve the interfacial compatibility focus more on the addition of various compatibilizers than on the structural modification of the natural fiber. In this paper, an attempt was made to enlarge the interfacial interaction areas of the recycled polyethylene (rPE)/wood flour (WF) composites by steaming the WF. Multi-monomer graft copolymers of polyethylene (GPE) were used as compatibilizers for the composites. How the enlarged interfaces affected the morphology, mechanical properties, water resistance, thermal stability, and dynamic rheological properties of the rPE/WF composites was investigated. The steaming process was able to enlarge the voids of the WF and therefore activate more interfaces for interactions. It was found that the interfacial morphology of the composites was affected by the degree of interfacial compatibility of the composites and so was characterized by various distinctive blossom shapes having a variation of compositions. With the help of GPE, the steaming process was able to significantly improve the interfacial compatibility of the composites and therefore improve the mechanical properties, water resistance, thermal stability, and dynamic rheological properties of the composites.