Cancer remains a leading cause of mortality worldwide, and the limitations of conventional treatments underscore the urgent need for more effective and targeted therapeutic strategies. Polymeric nanoparticles (PNPs) have emerged as highly versatile platforms for cancer therapy, offering tunable physicochemical properties, improved pharmacokinetics, and the potential for site-specific drug delivery. Recent advances in polymer chemistry and nanofabrication have enabled precise control over particle size, surface chemistry, and drug release profiles, facilitating passive and active tumor targeting, as well as responsiveness to tumor-specific stimuli. This review critically examines the design and functionalization of PNPs, their applications across chemotherapy, gene therapy, immunotherapy, and combination treatments, and the incorporation of multifunctional and theranostic capabilities. We also discuss the translational challenges—such as manufacturing scalability, tumor heterogeneity, and safety concerns—and explore emerging trends including biomimetic nanocarriers, AI-driven formulation optimization, and personalized nanomedicine approaches. By integrating recent findings from, this work provides a comprehensive overview of the current landscape and future opportunities for PNPs as next-generation cancer therapeutics.