The soil environment is an important reservoir for entomopathogenic fungi (EPF), which can significantly contribute to reducing the populations of soil-borne insects, including agricultural and forest pests. The objective of this study was to conduct a comparative analysis of the occurrence of EPF in soils from six selected post-agricultural afforestation sites and the adjacent cultivated fields and forest habitats. The research material comprised soil samples collected in spring and autumn 2023 in six localities within the area of operation of the Siedlce Forest District in the Masovian Voivodeship (Poland). A total of four genera of entomopathogenic fungi were isolated from the studied soils of adjacent habitats using selective media: Beauveria spp., Metarhizium spp., Cordyceps spp., and Akanthomyces spp. The occurrence of individual fungal genera and the density of their colony forming units (CFU) in the studied soils varied depending on the site, habitat type, and season. The highest number of CFU of fungal insect pathogens was recorded in soils from agricultural fields in both spring and autumn, followed by former agricultural afforestation, and the lowest number was recorded in soils from forest habitats. The dominant genus of entomopathogenic fungi, forming the most infectious units, in soils from post-agricultural afforestation and adjacent croplands was Metarhizium spp. In spring and autumn, the genus Beauveria dominated in forest soils from the six study sites, and in soils from post-agricultural afforestation, it formed more colonies than in soils from croplands.