Background and purpose: One of the most prominent concerns for the water consumers is pathogenic microorganism contamination. Wells and underground water resources are the main resources of drinking water in Sari city, Iran. The main objectives of the research project were to explore the distribution and frequency of mycoflora in wells and underground water resources of the city and their contamination effects on humans. Materials and methods: Three reservoirs and 18 wells or underground water resources were analyzed. Water samples were then filtered and analyzed according to the World Health Organization guidelines. Each filter and 0.2 ml of suspension inoculated on SDA+CG media. For fungal growth, plates were incubated at 27’C for 7-10 days. The fungi were identified by standard mycological techniques. Results: Fungal colonies were isolated from all samples. From total of 160 fungal colonies isolated from wells water, 14 species of fungi were distinguished. Rhodotorula (54.4%), Monilinia (13.7%), Alternaria (6.9%) were the most commonly isolated. Drechslera, Rhizopus, and Exserohilum (0.6%) had the lowest frequency. There was no significant difference between fungal elements isolated from three major reservoirs (P>0.05). Conclusion: This study revealed that resources of drinking water from an area have to monitored and if its fungal CFU be greater than a certain value, medical and health preventive measures should be taken before the water is used by human. In this context, public and private awareness should also be provided through the media, broadcasting, teachers and scholars.