A comprehensive study of the drain current drift mechanism and hysteresis phenomena in fabricated p-channel junctionless ion-sensitive field-effect transistor (JL-ISFET) has been investigated for the first time. The drift measurements have been performed through transient analysis of drain current, under different pH and liquid-gate bias (Vlg). Further, time-dependent gate-capacitance (CG) has also been analyzed to see the effect of hydroxyl ions (OH-) in the sensing film (Al2O3). The hysteresis has also been investigated for different pH loop ( 7 → 3 → 7 → 11 → 7 and 7 → 11 → 7 → 3 → 7) and times (960s, 1500s, and 1920s). It has been observed that the drift of JL-ISFET occurs because of chemical modification of the sensing film, due to OH- . The proposed device exhibits a threshold voltage sensitivity of 58.2 mV/pH that is near to the Nernstian limit. Further, the hysteresis width and maximum drain current drift are measured as ~1.3 mV and 2.4 µA (~75%), respectively.