In this work, a field effect transistor (FET) based biosensing platform was developed to detect hydrogen sulphide in human saliva directly. A highly sensitive FET-based biosensor fabricated utilizing layered transition metal dichalcogenides (TMDs) MoSe2 as a channel layer. Hydrogen sulphide (H2S) has physiological and pathological relationships with human health; rapid and real-time detection of H2S in human body fluid is necessary. The present biosensing device is appropriate for point-of-care applications that require quick and real-time detection of H2S in saliva. The lowest detection limit for the fabricated sensor is 1 µM with the maximum sensitivity of 68% at the lowest concentration. The current results show linear changes in the concentration range of 1–100 µM. However, the fabricated sensor is suitable for all kinds of sulphide (H2S, HS-, S2-) detection in human biological fluids.