AbstractDual‐gate field‐effect transistors (FETs) based on organic semiconductor polymer and SiOx as the topmost active sensing layer permit monitoring of pH in physiologically relevant conditions in a fast and reversible fashion. Beyond that, due to the bottom gate‐induced field effect, such sensors exhibit tunable sensitivity and provide faster continuous measurements compared to conventional bulky glass bulb pH sensors. pH response of bare SiOx is evaluated independently by means of voltmeter measurements. When assembled in dual‐gate architecture, the pH response of FET devices scales in agreement with the theoretical model, which assumes capacitive coupling, exhibiting an amplification of up to 10. This opens up the possibility for reversible and reliable sensing based on organic semiconductors well beyond pH sensors.