This chapter analyzes the transformative impact of biosensors and aptamers on cancer diagnosis and treatment. It emphasizes the importance of early detection and examines the limitations of traditional diagnostic methods. The chapter explains biosensors’ key components and mechanisms, introducing aptamers and highlighting their advantages over antibodies. It explores how aptamer-based biosensors detect cancer biomarkers and presents case studies demonstrating their clinical value. The therapeutic potential of aptamers in targeted therapies and personalized medicine is also discussed. Finally, the chapter reviews current innovations, including nanotechnology integration, and emphasizes the ongoing research needed to fully harness the potential of biosensors and aptamers in cancer care.