Plasmonic nanomaterials have revolutionized the field of biosensing by enhancing sensitivity and specificity in the identification of biological molecules, pathogens, and biomarkers. Particularly, accurate and sensitive diagnosis with plasmonic nanomaterials is crucial for effectively treating various types of cancers. Noble metal nanoparticles, dielectric nanomaterials, graphene, and semiconductor nanocrystals offer diverse options for biosensing applications, enabling ultrasensitive sensing and multicolor imaging. However, challenges such as energy dissipation, photobleaching, field confinement, and biocompatibility persist. These challenges are being addressed by ongoing research and innovation, which offer the promise of integrating multiple plasmonic materials to create hybrid systems for revolutionary breakthroughs. This chapter includes categorized sections that describe nanobiosensors based on plasmonic materials, such as metal nanoparticles, dielectric nanomaterials, graphene, and semiconductor nanocrystals, for cancer diagnosis.