The extraordinary physiochemical properties of carbon nanotubes (CNTs) stimulated their wide application in biosensing research. Nanotube characteristics of fast electron transport, large surface area, high strength, excellent catalytic activity and good chemical stability contribute to ultrasensitive, highly selective and stable CNT biosensors. Among the various CNT biosensors, the field-effect transistor (FET) architecture has received tremendous attention due to the advantages of high performance, miniaturization, and capability for mass production. In this paper, we address recent advances in the development of CNT biosensors based on FETs. The synthesis and properties of CNTs are discussed, along with their integration into biosensors. Recent progress in device fabrication, including CNT functionalization, attachment, and bioreceptor immobilization in CNT-based FET biosensors are highlighted. Examples in medical, food and environmental fields are illustrated.