Objectives: Research background and objective: Having access to safe drinking water has an essential role in ensuring public health. Ignoring damages caused by failures in water distribution system leads to water contamination. This study intended to investigate the bacteriological quality of drinking water of water coolers in four hospitals of Razi, Heshmat, Al-Zahra and Aria in Rasht Township. Methods: In order to meet the objective of the study, 13 water coolers located in these hospitals were randomly selected. The values of total coliforms, heterotrophic bacteria, residual chlorine, pH, and turbidity were measured. The data were analyzed using Excel and SPSS.  Results: The findings showed a strong relationship existed between pH values of input and output water (R=0.55), but that for turbidity was insignificant (R=0.13) (p=0.42). In two cases, coliform bacteria were observed, too. The value of HPC in tested samples was less than 15 cfu/ml before entering and after leaving water coolers. Conclusion The results indicated absence of coliform bacteria. The reduction of residual chlorine after the water filtration system in water coolers indicated low-level of contamination in water coolers. Therefore, regular servicing and monitoring water coolers and their connections would ensure health of staff members, patients and all who enter hospitals.