In vitro models for drug delivery systems play a crucial role in pharmaceutical research by providing controlled environments to study the behavior and efficacy of drug formulations. These models typically involve simulated biological systems or tissues that allow researchers to assess drug release kinetics, stability, and interactions with biological barriers such as cell membranes. By mimicking physiological conditions in a controlled manner, in vitro models help in optimizing drug formulations for improved delivery efficiency and therapeutic outcomes. They are instrumental in screening potential drug candidates, assessing toxicity levels, and understanding mechanisms of drug absorption and distribution within the body. Overall, in vitro models serve as indispensable tools in developing and evaluating novel drug delivery systems, bridging the gap between early-stage research and clinical applications. This comprehensive review explores various in vitro models, including cell cultures, tissue explants, and organ-on-a-chip technologies, highlighting their applications, advantages, limitations, and prospects. Through understanding these models, researchers can enhance the design and efficacy of DDS, ultimately improving therapeutic outcomes.