Environmental hazards related to the weathering of iron sulfides in technogenic soils (Technosols) developed on sulfide-bearing mine wastes were investigated. The soil profiles studied were located on mine spoils of three abandoned industrial sites in Poland: the “Siersza” hard coal mine in Trzebinia, the “Staszic” pyrite mine in Rudki, and pyrite mines in Wieściszowice. The soils investigated were weakly developed and strongly acidic, unless neutralizing agents were present, and they contained large amounts of total sulfur, also in the form of sulfides. In some horizons of young soils from Trzebinia and Rudki, sulfide sulfur was the predominant form of sulfur. Iron sulfides in these soils were relatively poorly weathered, whereas in old soils from Wieściszowice sulfides were almost entirely weathered. The presence and weathering of sulfides in all of the soils investigated causes a risk of long-term acidification process. The study revealed the occurrence of high amounts of heavy metals and radioactive elements in investigated soils. Such properties of soils like strong acidity, as well as high contents of trace elements and sulfur (also occurring as sulfides), should be considered during reclamation and management of mine spoils containing iron sulfides.