This study was carried out to determine the influence of tides to the quality of cave water in Zanzibar Island, part of Tanzania. It was to establish the effect of tidal change on the cave water quality using pH, temperature, EC, TDS, and nutrients (NO3-N, NH3-N, PO43-) in the water as indicators. Overall results indicated that, the cave water quality changes with tides regardless of the fluctuation of the investigated parameters. Moreover, most of the tested parameters were not in range compared to those proposed by World Health Organization (WHO). This confirms that the quality of the cave water has been influenced by low and high tides due to high intrusion of the sea water entered in the caves.