The discovery of the glymphatic system (GS) transformed understanding of central nervous system homeostasis by revealing a brain-wide network that facilitates cerebrospinal and interstitial fluid exchange along perivascular pathways. This system clears metabolic waste and maintains the precise ionic environment required for neuronal function through the coordinated action of astrocytic aquaporin-4 channels and intact perivascular architecture. Glioblastoma multiforme (GBM), the most aggressive primary brain tumor in adults, alters physiological barriers through pathological angiogenesis, compression of perivascular spaces, depolarization of aquaporin-4 at astrocytic endfeet, and obstruction of venous and lymphatic drainage. This narrative review synthesizes current experimental and clinical literature identified through targeted searches of PubMed and Scopus to examine interactions between glioblastoma, glymphatic system dysfunction, and tumor microenvironmental changes. To minimize selection bias, studies were categorized according to evidence source and experimental design. Evidence from rodent models and advanced imaging demonstrates as tumor growth impairs glymphatic function, the resulting dysfunction promotes tumor progression by enabling accumulation of pro-tumorigenic growth factors, inflammatory mediators, and acidic metabolites, while elevated interstitial fluid pressure limits drug delivery. Impaired antigen drainage further diminishes immune surveillance, contributing to the immunosuppressive microenvironment that limits immunotherapy efficacy. A critical evaluation of these mechanisms highlights how the glymphatic system influences disease progression and suggests novel avenues for diagnostic imaging and therapeutic intervention. Although significant challenges remain in modeling human fluid dynamics, understanding these hidden networks offers a promising frontier for strategies aimed at restoring cerebral clearance and improving clinical outcomes.