The past two decades have evidenced a tremendous growth in the field of responsive polymers, which can exhibit reversible or irreversible changes in physical properties and/or chemical structures to an external stimulus such as pH, temperature, ionic strength, light irradiation, mechanical forces, electric and magnetic fields, specific analytes, external additives (ions, bioactive molecules, etc.), or a combination of them. Responsive polymers can exist in the form of solutions, gels, self-assembled nanoparticles, (multilayer) films, and bulk solids. The field of responsive polymers has nowadays evolved well beyond the demonstration of novel and interesting properties. Currently, the exploitation of useful and advanced functions, e.g., drug or gene carriers with triggered release properties, catalysis, detection and imaging, environmentally adaptive coatings, and self-healing materials, has emerged to be a more relevant subject. In this Perspective, we focus on recent developments of responsive polymer-based chemo- and biosensors, highlighting this concept with selected literature reports. Such functional polymeric materials show prominent advantages such as tunable detection sensitivity, structural stability, aqueous dispersibility, biocompatibility, processability, and facile integration into detection devices, as compared to their small molecule analogues.