In most developing countries, uncontrolled solid waste disposal has co  ntributed to serious environmental problem which has led to a significant degradation of soil, thereby constituting heavy metal pollution. The research examined the seasonal differences in the physicochemical characteristics and the heavy metals contents of the soils at the Auta Gurgu abandoned solid waste dumping site in Karu L.G.A. of Nasarawa state of Nigeria in the rainy and dry seasons. Standard laboratory tests were performed on composite soil samples of the solid waste dumpsite and the control site in determining the pH, electrical conductivity, nutrients, organic matter indices, particle size distribution, and selected metals. One-way analysis of variance was used to test the statistical differences between the dumpsite and control soils at = 0.05. Findings indicated that electrical conductivity, nitrogen, nitrate, phosphate, sulphate, and organic matter of dumpsite soils were higher than control soils in both seasons though overall, the higher levels were found in the dry season. Soil compositions in dumpsites were highly contaminated with heavy metals; Zn, Pb, Cr, Cu, Cd and Ni, compared to control levels, which characterises anthropogenic contributions of solid waste decomposition. Seasonal variability also affected the physicochemical parameters as well as the distribution of metals as the results of the leaching, evaporation, and waste minerals mineralization processes. The results present the long-term contamination possible of the old dumpsites and the importance of establishing effective waste management practices, scheduled environmental inspections, and remedial measures to reduce the hazards to human health and the environment.