Core–shell structures have emerged as gifted photocatalytic systems for defending the reactive core materials from the surrounding reactive substances. By integrating various functional materials, it provides maximum interfacial connectivity among various components to bolster catalytic efficacy and material stability. Graphitic carbon nitride (g-C3N4), characterised by its unique two-dimensional structure, plentiful active sites, excellent stability and tunable electronic properties, is well-suited for constructing core–shell nano-heterojunctions with enhanced interfacial contact. This chapter systematically outlines the advantages of employing g-C3N4-based core–shell structures, delving into their classification and fabrication methods, which include the reflux method, self-assembly method, hydrothermal method and calcination/ heat treatment method based on recent studies. It meticulously examines the characterisation and properties associated with g-C3N4-based core–shell nanoparticles. Moreover, it seeks to provide fresh insights and perspectives on the potential of g-C3N4-based core–shell structures for photocatalytic hydrogen production and pollutant degradation, underscoring their significance for future research and applications in this domain. Finally, the review concludes by addressing future prospects and challenges in this realm, emphasising strategies to augment catalytic efficiency and proposing new research avenues to stimulate further progress.