Atmospheric pollution has increased worldwide during the last decades affecting forest ecosystems. Thermal power plants give off high levels of contaminants, which can damage forest health. Bioindicators can be helpful tools used for evaluating environment changes by giving an accurate measure of the extent of pollution. The focus of this study was to analyse fungal mycoflora in Pinus sylvestris stands near a thermal power plant and the possible correlation between the presence of the fungi and the air quality as measured by lichens and mosses. Fungi associated with pine needles were selected as subjects of this study because of their phytopathological importance and association with the pine trees' decline. Samples for this study were selected from eight plots in close proximity to a thermal power station in northern Spain. Symptoms of decline were previously observed in all the plots before sampling was performed. Lichens were used as bioindicators of environmental quality in two ways, first using the Index of Atmospheric Purity and second through categorization of lichen species based on their sensitivity. In addition, botanical quality was measured regarding the presence or absence of mosses. With two seasonal samplings (autumn and spring) and the use of four types of pine needle plant material (green needles, dried needles, half-green, half-dried needles and fallen needles), both endophytes and epiphytes present in the needles were isolated and observed. Thirty fungal species in total were identified of the 1095 isolates obtained. Furthermore, significant differences in fungal isolates were observed between seasons and among the different plant material. Results showed that both environmental air quality and botanical quality were negatively correlated with the relative isolation frequency of fungi. The higher number of isolates was attributed to a possible infection produced by fungi, which could be a leading factor in the trees' decline.