Receptor-mediated endocytosis is essential for targeted gene/drug delivery to a specific cell type. In this study, we developed a capacitance sensor to monitor receptor-mediated endocytosis in real time. The capacitance sensor was able to detect a capacitance peak in different cell lines during the internalization of adenoviruses or antibodies via receptor-mediated endocytosis. In contrast, the capacitance declined without a capacitance peak when nanoparticles were taken up via non-specific pinocytosis. Thus, our capacitance sensor represents a potential capacitance-based means of discrimination between receptor-mediated endocytosis and non-specific pinocytosis. Moreover, we developed a capacitance sensor array to demonstrate capacitance-based high-throughput screening. We showed that the capacitance sensor array could rapidly identify antibodies or ligands with high specificity for target molecules. We propose that the capacitance sensor array will provide a valuable tool for high-throughput screening.