Organic field‐effect transistors (OFETs) are the central building blocks of organic electronics, but still suffer from low performance and manufacturing difficulties. This is due in part to the absence of doping, which is mostly excluded from OFET applications for the concern about uncontrollable dopant diffusion. Doping enabled the modern semiconductor industry to build essential components like Ohmic contacts and P–N junctions, empowering devices to function as designed. Recent breakthroughs in organic semiconductors and doping techniques demonstrated that doping can also be a key enabler for high‐performance OFETs. However, the knowledge of organic doping remains limited particularly for OFET use. Therefore, this review addresses OFET doping from a device perspective. The paper overviews doping basics and roles in advanced complementary technologies. These fundamentals help to understand why and how doping provides the desired transistor characteristics. Typical OFETs without doping are discussed, with consideration for operating principle and problems caused by the absence of doping. Achievements for channel, contact, and overall doping are also examined to clarify the corresponding doping roles. Finally, doping mechanisms, techniques, and dopants associated with OFET applications are reviewed. This paper promotes fundamental understanding of OFET doping for the development of high‐performance OFETs with doped components. Doping specifically for organic transistor applications from a device perspective is reviewed. Doping fundamentals, various doping roles in transistors, different operating principles, relevant issues caused by the absence of doping in typical organic transistors, organic transistor doping achievements to date, doping mechanisms, techniques, and dopants are systematically discussed.