To date, hydrogels have gained attraction due to their inherent advantages such as wide selection of precursors and additives, low toxicity, easy shape control, and biological compatibility. Therefore, extensive studies are being conducted for their application in diverse fields. In this review, recent impressive studies on the use of tailored hydrogel materials for biosensor applications have been summarized. As the hydrogel precursors and the sensing mechanisms are wide and extensive, we have summarized chemical/biological sensors depending on the hydrogel precursors possessing biocompatible features. Hence, versatile biological/biochemical sensors using conventional hydrogels based on carbohydrates, polymers, DNA and peptides have been covered primarily. In addition, emerging conductive hydrogels possessing conducting additives such as graphene, conducting polymers, and nanocrystals have been introduced and their application in biosensors has been described extensively. Sensor operations are dependent on the changes in resistance and conductance, signal transduction through electrodes, sensor geometry, and interactions between sensing media and target analytes. As we primarily focused on the type of precursor materials and the sensor performance such as sensing mechanism, sensitivity, linear range, and selectivity was summarized and presented. A trend in the research fields of hydrogel-based elaborate sensors has also been briefly described. This article provides essential information for advanced research in related fields.