The degradation of tebuconazole in the majority of Polish mineral soils with low organic carbon content is slow, and its adsorption is especially low in subsoils. Therefore, the fate of tebuconazole in these soils cannot be predicted based on results of adsorption and degradation experiments carried out in typical soils of the European Union. For this reason, simulations of tebuconazole accumulation in Polish soils and its leaching to groundwater were carried out. The cultivation of winter cereals and winter oilseed rape was simulated using FOCUS PELMO in six Arenosol, Luvisol, and Chernozem profiles, representing 59% of Polish arable mineral soils. The simulations indicated that almost all fungicide that reached the soil surface was retained in the topsoil layer of 0–15 cm. The highest concentrations (range of 0.069–0.320 mg/kg) were estimated for the layer 0–5 cm. The results suggested that runoff can be the principal source of tebuconazole in surface water. It was found that the majority of tebuconazole that reached the soils was microbiologically degraded. However, in years with weather conditions that were unfavorable for degradation, up to 11% of tebuconazole that reached the soils remain undegraded. In addition to the accumulation of tebuconazole in the topsoils, the simulations indicated its very slow but constant penetration into the subsoils. The estimated concentrations of tebuconazole in percolate water were low: < 0.02 μg/L at the depth of 25 cm, < 0.002 μg/L at the depth of 75 cm, and trace concentrations at the depth of 1 m in one profile. The obtained results were consistent with results of monitoring studies available in literature.