Glioblastoma multiforme (GBM) remains one of the most aggressive and resistant to treatment types of brain cancer; hence, new therapeutic approaches are required. Recent advances in nanomedicine have positioned graphene quantum dots (GQDs) as promising candidates for targeted cancer therapy due to their exceptional physicochemical properties, biocompatibility, and multifunctional capabilities. This review examines how GQDs can be included in multifunctional nanocomposites and how they might be used to diagnose and treat GBM. We discuss the unique structural and optical characteristics of GQDs that facilitate blood-brain barrier penetration, targeted drug delivery, bioimaging, and photothermal/photodynamic therapy. The design techniques of GQD-based nanocomposites are emphasized, along with their stimulus-responsive behavior, drug-loading efficiency, and surface functionalization. The cytotoxic effects on glioblastoma cell lines, biodistribution, and biosafety profiles are also rigorously assessed, along with in vitro and in vivo research. There is also discussion of toxicity issues, scalable synthesis, and limited clinical translation. This review highlights the transformative potential of GQD-integrated nanocomposites as a next-generation therapeutic platform for effectively managing GBM.