The present study aimed to assess the effects of climate change on the toxicity of metal-polluted soils. Bioassays with Enchytraeus crypticus were performed in soils polluted by mine wastes (mine tailing, forest, and watercourse) and under different combinations of temperature (20 °C and 25 °C) and soil moisture content (50% and 30% of the soil water-holding capacity). Survival and reproduction were set as endpoints. No effect was observed on survival (average survival ≥ 80%). Reproduction was the most sensitive endpoint, and it was reduced between 65% and 98% compared with control after exposure to watercourse soil (lower pH, higher salinity, and higher available metal(loid) concentrations). In this soil, effective concentrations at 50% and 10% (EC50 and EC10) significantly decreased with decreasing soil moisture content. In general, the worst-case scenario was found in the driest soil, but the toxicity under a climate change scenario differed among soil types in relation to soil properties (e.g., pH, salinity) and available metal(loid) concentrations.