Safe delivery of drugs inside living organism is always a great challenge. Drug intake below and above prescribed limits may cause unseen and severe health problems. In addition to the amount of dose, another critical issue is to deliver drugs inside the body. Preferable drug delivery modes are oral, inhalation, nasal, rectal routes, or via injection. Further, there are situations when a drug has to be released over a specific duration in a controlled mode. In order to have scientific solutions to the problems and challenges faced, researchers have come up with various drug delivery devices. This field has resorted to various micro-fabrication techniques and fluidic principles coupled with the assistance of electrical and mechanical engineering knowledge. It has observed a series of developments in device optimization. These devices have been developed for real-time monitoring and measurement of drug delivery and thus may have several components (micro-pump, micro-needles, microfluidic channels, micro-sensors, essential electronic circuits, and so on). Keeping up with the vast development in the field of drug delivery devices, this chapter provides an insight into the basics of various drug delivery devices, their principles, description of various components used in the micro-electro-mechanical system (MEMS) device manufacturing, along with the state-of-the-art review of existing MEMS-based drug delivery devices. © 2019 Elsevier Ltd. All rights reserved.