A large number of fungi are present in poultry houses. Conditionally pathogenic molds of the genus Aspergillus are among the most common fungi found in both houses and poultry. This investigation tried to clarify the contradictory results of previous studies on the higher occurrence of fungi in poultry farming during cold and warm periods of the year, respectively. The study was conducted in a broiler house, under commercial production conditions, during 36-day production cycle in warm (July-August) and cold (December-January) periods of the year. The house is of enclosed type, with controlled microclimate. During each cycle, there were 18,000 chickens of Ross hybrid in the house kept on deep litter containing chopped straw and sawdust, with stocking density of up to 33 kg/m2. The microclimate conditions, air-borne gaseous and corpuscular contamination in the poultry house, litter quality, the occurrence of particular fungi in the air, litter, feed and chickens, as well as their activity were measured weekly. Throughout the study period, microclimate conditions and the occurrence of air-borne fungi were determined at 5-m and 25-m distances from the house as well. The results obtained showed the relative air humidity inside the house, the concentrations of ammonia, carbon dioxide, air-borne bacteria, and fungi in the chicken trachea and esophagus to be significantly higher (P<0.05) on average in winter compared to summer. In summer period, significantly higher (P<0.05) average litter temperature and concentrations of fungi in indoor air and chicken feed were recorded. The season had no impact on other parameters observed, indoor air temperature and airflow rate, dust concentration, litter moisture, pH and fungi concentration, and broiler activity. The following fungi were found in the study: Alternaria sp., Aspergillus sp., Cladosporium sp., Fusarium sp., Mucor sp., Penicillium sp., Rhizopus sp., Trichophyton sp. and yeasts. The genus Aspergillus encompassed five species: A. flavus, A. fumigatus, A. niger, A. terreus and A. versicolor. The season had impact on the qualitative structure of fungi. The yeasts were the most frequent finding in both seasons; yet, more frequent (P<0.05) in chicken environment during summer, and in chickens during winter. Regarding molds, the predominant genera on average (P<0.05) were Aspergillus and Cladosporium in summer, and Penicillium and Mucor in winter. At the same time, these fungi were most frequently isolated in the study. Study results suggest that fungi in broiler environment are less frequently found during cold period of the year, but with a higher frequency in chickens, attributing this finding primarily to relative air humidity. As in this study, the higher indoor relative air humidity in the winter period was mainly the result of higher outdoor humidity, study results also point to a conclusion that the area in which the poultry are raised has a major role in the occurrence of fungi in their environment, and consequently in themselves. Study results also suggest that microclimate conditions in poultry houses are worse in the winter period, implying not only a detrimental effect on animals, but also on the health of humans working in these environments. Moreover, it is concluded that different fungi, i.e. their concentrations, are expected to be found in different seasons. In this study, molds of the genus Aspergillus as one of the most pathogenic fungi and with a zoonotic potential in addition, were determined in higher concentrations during summer, implying that this season also carries a risk when it comes to fungal diseases