<p>Early cancer diagnosis has become one of the prominent challenges in recent years. Conventional diagnostic methods such as ultrasound, X-ray, bone scan, and computed tomography lack sensitivity for early-stage cancers and often involve high costs and invasive procedures. Therefore, identifying specific molecules indicative of cancer (biomarkers) is critical for early diagnosis and effective treatment planning. Fluorescent biosensors have emerged as a promising approach for early cancer detection, disease monitoring, and treatment management. The present review delves into the latest developments in nanomaterial-based fluorescent biosensors for cancer biomarker detection. It explores the potential of nanomaterials, including metal-based nanoparticles, up-conversion nanoparticles, quantum dots, carbon nanostructures, and luminescent metal-organic frameworks for sensor development. A performance evaluation of the biosensors based on key quality measures (such as detection limits, linear range, and efficiency) is also summarized. Finally, the review addresses the current challenges and future directions in overcoming technical hurdles in cancer diagnostics.</p> Graphical abstract <p></p>