Conductive polymers (CPs) are a type of organic materials that combine the flexibility and processability of polymers with the electrical properties of inorganic semiconductors, making them highly suitable for sensor development. These materials, including polyaniline, polypyrrole, polythiophene, and PEDOT, exhibit unique electrical, optical, and chemical properties, enabling their use in the design of highly sensitive and selective sensors for a broad range of environmental, industrial, and biomedical applications. The conductivity of CPs is derived from their conjugated structure, which can be “tuned” through doping and functionalization to optimize the performance of various sensing materials. This systematic review provides a comprehensive examination of the synthesis techniques, conductive mechanisms, and structural modifications that make CPs effective in chemical, gas, and biosensors. It discusses how CPs, which have significant advantages in terms of selectivity and responsiveness, enable real-time, high-precision detection of chemical and biological analytes. The paper also categorizes the types of sensors made with CPs, including chemical sensors for pollutant detection, gas sensors for CO₂, CO, and NH₃ sensing, and biosensors for medical diagnostics like glucose monitoring. In addition, this systematic review addresses important issues such as enhancing sensor sensitivity, selectivity, and stability over time, all of which are significant in providing dependable performance in practical applications. This systematic review highlights the significance of conductive polymers in developing sensor technologies and promoting innovation in fields ranging from environmental monitoring to biomedical diagnostics by addressing current advancements and identifying future research directions.