Thousands of billions of dollars have been disbursed worldwide for the diagnosis and therapy of disease. Nanobioscience combined with sensing technology has facilitated the pathway to diagnosis by introducing a novel, highly sensitive and selective detection system known as the nanobiosensor to reduce the overall cost of treatment. Among the many types of biosensors, optical ones are more easily developed because of their low cost, rapid construction, small size, high performance, high sensitivity and selectivity, high signal-to-noise ratio, flexible geometry, and portability properties. This study reviews and discusses nanobiosensors and electrochemical biosensors with the main focus on colorimetric, fluorometric, luminometric, fiber optic, and surface plasmon resonance-based optical biosensors and an emphasis on their applications in medical diagnosis.