<p>Biosensors based on thin-film transistors (TFT) have been the major area of interest especially with metal oxide semiconductors and organic semiconductors as the platform to introduce the next-generation biomedical diagnostics. They have several inherent strengths such as high sensitivity, chemical stability, biocompatibility, ease of surface functionalization, and the ability to be processed using low-cost, high-scale production techniques, which makes them useful in continuous and point-of-care health monitoring. Metal oxide semiconductor TFTs have advantages of relatively easy fabrication in a solution process or sputtering process and advantages for integration into very large sensor arrays. In the meantime, other advantages of organic transistors include mechanical flexibility and outstanding biologic compatibility. Even though the sensitivity and selectivity of biosensing is currently not optimal, relatively new progress in designing materials and engineering devices has made it possible to create very efficient biosensing devices. This review points out the prevalent methods and recent development on the combination of oxide and organic semiconductors in the form of TFT biosensors, emphasizing the process of fabrication, surface modification, and real-world application as an example of biosensing.</p>