In the present work, gold nanoparticles (Au NPs) were synthesized on indium tin oxide (ITO) thin film on glass substrate for the pH sensing application based on extended gate field effect transistor (EGFET). The ITO thin film was deposited on glass using RF sputtering and then the Au NPs were synthesized on it by pulsed laser ablation in liquid (PLAL) technique. The Au NPs were characterized using transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopic techniques. From the TEM analysis, the size of the spherical shaped Au NPs was found to be in the range of 5–22 nm. The UV-Vis spectroscopy analysis revealed absorption peak at 518 nm, indicating purplish red color. The XPS data revealed Au 4f doublet binding energy peaks of the photoelectrons at 83.79 and 87.45 eV. The current-voltage (I-V) curves indicated pH sensitivities values of 43.6 mV/pH and 0.6 \({\left(\mu A\right)}^{\frac{1}{2}} /pH\) with linear regression of 0.9. The hysteresis and drift characteristics of Au NPs/ITO/G membrane were also studied to investigate its stability and reliability. The results of this work demonstrated that the Au NPs/ITO/G membrane is quite useful for the acidity and basicity detection.