pH is a significant parameter in both biological and environmental fields. Numerous commercially available metal/metal oxide electrode-based pH sensors are losing popularity having drawbacks such as mechanical brittleness, inflexibility owing to size, high energy consumption, and high cost. The primary factors influencing their utilization are their capacity to retain charges as well as their electro-catalytic, electro-chromic, and photo-electrochemical capabilities. Toxicology of materials, interference from other ions or analytes, affordability, and adaptability of the materials are the major obstacles when devising sensors for practical applications. Tungsten oxide (WO3) is a potential hydrogen-sensitive substance for monitoring pH over a large range. Because of its simplicity in morphological and structural control, reversible change in conductivity, selectivity, high sensitivity, and bio-compatibility, as well as the fact that it works well in ambient and deoxygenated environments, it is good for biomedical applications. Therefore, in this chapter, the discussion is on (i) current progress of WO3 nanoparticles-based pH sensors, (ii) synthesis of WO3 nanoparticles, and their application in developing pH sensors, (iii) various characterizations of pH sensors based on WO3 nanoparticles, (iv) future perspectives of WO3 based pH sensors.