The pH in tumour cells and the tumour microenvironment has played important roles in cancer development and treatment. It was thought that both the extracellular and intracellular pH values in tumours are acidic and lower than in normal cells. However, recent progress in the measurement of pH in tumour tissue has disclosed that the intracellular pH (pH_i) of cancer cells is neutral or even mildly alkaline compared to normal tissue cells. This review article has summarized the recent advancement in the measurement pH_i and extracellular pH (pH_e) in cancer cells, and the effect of pH_i and pH_e on proliferation, migration and biological functions of cancer cells. This paper has also elaborated recent treatment strategies to manipulate pH_i and pH_e for cancer treatment. Based on the recent progress in pH_i and pH_e manipulation in cancer treatment, we have proposed potential nanoparticle-based strategies to manipulate pH_i and pH_e to effectively treat cancer.