Natural fiber–reinforced plastics (NFRPs) are gaining attention due to increasing concerns about environmental pollution and energy efficiency. However, low-dimensional stability due to the high water absorption of natural fibers and poor interfacial bonding between natural fibers and the polymer matrix limit their use of NFRPs. In this study, nano/micro hierarchical structures and surface plasma treatment were introduced into NFRPs with a layer-by-layer (LbL) structure to address these drawbacks. A fibrous preform combining lyocell fiber (LF) and cellulose nanofibril (CNF) was fabricated, where CNF enhanced mechanical strength and moisture stability. Biodegradable polybutylene succinate (PBS) and the preform were hot pressed to fabricate LbL-structured PBS-LF/CNF NFRPs. The interfacial compatibility between PBS and the fibrous preforms was improved by hydrophilic plasma treatment of the PBS surface, and an increase in the moisture stability and tensile strength of the NFRP was observed. Ultimately, the NFRP with the CNF binder and hydrophilic plasma treatment showed improved mechanical properties, with a modulus of 980 %, tensile strength of 430 %, and toughness of 270 %, compared with neat PBS. In addition, PBS-LF/CNF NFRP biodegraded in a compost environment. These results suggest that PBS-LF/CNF NFRP can be used as a sustainable composite material in versatile industrial fields.