The fundamental principles of flow-through optosensors, together with the most significant procedures and alternatives developed in the applications of flow-through optosensors to pharmaceutical analysis are reviewed. The most frequently used solid sensing zones, flow-through cells, manifolds, regeneration step and types of detection are considered. Single parameter, biparameter, and multiparameter sensors developed are reviewed and their most relevant features presented. Finally, a critical comparison with other analytical methodologies/techniques is performed and the potential of flow-through optosensors in pharmaceutical analysis and their future trends discussed.