Seasonal and altitudinal variations in the abundance and diversity of soil arthropods were investigated in a pure Abies nordmanniana subsp. bornmulleriana (Uludag fir) forest ecosystem. Sample plots were set at three different altitudes (1,200 m, 1,400 m and 1,550 m), and samplings were performed in four seasons in February, May, August and November in 2010. Soil properties varied significantly among the seasons; higher soil nitrogen (N) and carbon (C) concentrations were found in summer while C/N ratio and pH were higher in autumn. Litter mass decreased from winter to summer; however, litter nitrogen concentration was inversely correlated with litter mass. Litter C/N, potassium and magnesium concentrations were different among the seasons although litter pH, carbon, phosphorus and calcium concentrations did not show significant differences. Soil pH, phosphorus, calcium and magnesium concentrations mainly showed a decreasing trend with altitude; however, soil nitrogen and carbon concentrations had a significantly increasing trend. Litter mass did not have any significant difference although litter pH, calcium and magnesium concentrations showed a significantly decreasing trend with altitude. In total, 54,348 individual soil arthropods were counted, identified and classified from 144 litter and soil samples collected in the study. The arthropods that were identified belonged to 90 different taxa within six classes and 28 orders, which were significantly different depending on habitats (soil or litter), altitudes and seasons throughout the year.