Concentrations of fungal spores constitute a significant amount in bioaerosol depending on geographical regions and seasonal variations. Mycotoxin producing spores have adverse effects on humans. The aim of the study was to evaluate the prevalent species of airborne fungi in the indoor environment of the Shyambazar Metro-Railway Station, Kolkata, India. This area is below the ground level and fully surrounded, with constant movement of commuters. It is warm and humid with temperature and humidity ranges of 26.8 to 35.9 degrees C and 50 to 88.3% respectively. Air sample was collected for four months within the interval of two weeks by means of gravitational settling method via Petri dishes with Potato Dextrose Agar (PDA) culture media. Those fungi colonies that formed after an incubation period of 3 to 5 days at 25 to 28 degrees C were determined on the basis of micro and macro morphological characteristics. In this investigation, among fourteen spore types, Aspergillus niger was the most prevalent fungal genera followed by Aspergillus flavus and Penicillium sp. In addition, five sterile types and one unidentified species were also detected. The variation in the number of fungal colony was observed after every two weeks, in the summer months. The results of this investigation appeared to be quite significant for taking corrective measures.