• A discontinuous layered GNPs–ZrB2/AA6111 composite achieved high in-plane thermal conductivity of 230 W/(m·K), exceeding the matrix value of 206 W/(m·K).
• The composite exhibited pronounced anisotropy, with through-plane conductivity reduced by the low intrinsic through-plane conductivity of GNPs and increased interfacial thermal resistance.
• Tightly bonded GNP/Al interfaces, locked by CuAl2 nanoparticles, enabled GNPs to fully exploit their high in-plane thermal conductivity.
• The study provides a thermal conductivity model for two-phase nanoparticle-reinforced composites, supporting design of structure-functional integrated AMCs for thermal management applications.