ABSTRACT This study investigates low‐density green polyethylene (LDPE) nanocomposites reinforced with bamboo‐derived cellulose nanocrystals (CNCs) and compatibilized with polyethylene‐graft‐maleic anhydride (PE‐g‐MA). Four materials were prepared by melt extrusion and injection molding (neat LDPE; LDPE with 1.0 and 1.5 wt% CNCs; and LDPE with 1.0 wt% CNC + 1.0 wt% PE‐g‐MA) and evaluated by thermal, mechanical, and structural analyses. Fourier‐transform infrared spectroscopy (FTIR) indicated interactions between maleic‐ anhydride groups and CNC hydroxyls, supporting improved interfacial compatibility. X‐ray diffraction (XRD) showed increased crystallinity in CNC‐containing samples, consistent with a nucleating effect. Thermogravimetric analysis/derivative thermogravimetry revealed single‐step LDPE decomposition with an upward shift of the degradation‐rate peak upon CNC addition; residues remained below at these low loadings. Under uniaxial tension, stiffness increased significantly at 1.5 wt% CNC and in the compatibilized composite, while tensile strength improved only with PE‐g‐MA; elongation decreased with CNCs irrespective of compatibilizer, remaining highest for neat LDPE. After accelerated aging (UV + humidity), modulus and strength exhibited modest declines across all materials, comparatively larger in the compatibilized system, suggesting time‐dependent changes at the CNC‐matrix interface. Overall, bamboo‐CNC/PE‐g‐MA provides a sustainable route to tailor thermal performance and load‐bearing response of LDPE for applications that prioritize stiffness and thermal resistance over ductility.