This paper presents a study on the stabilization of contaminated soil deposits using fly ash (FA), quick lime (QL) and blast furnace slag (BFS). The soil samples were collected from a landfill site at Arupota, near EM Bypass, Dhapa, Kolkata. The soil was found polluted with heavy metals viz. Zn, Pb, Cu and Cr. The maximum dry density (MDD) and unsoaked California Bearing Ratio (CBR) values of the soil were found 1320 kg/m3 and 4.82% respectively. An attempt was made to immobilize the contaminants as well as improve the characteristic strength in the soil simultaneously through mechanical mixing with stabilizers. The factor-based Box-Behnken design (BBD) of Response Surface Methodology (RSM) was applied to examine the combined effect of selected additives that is, FA (5–20%), QL (5–20%) and BFS (5–20%), on soil MDD and CBR values which were considered as response functions. The predicted values of MDD and CBR in the model were found to be in close agreement with experimental values (R2 = 0.8265 and 0.9371 for MDD and CBR respectively). The optimum values of FA, QL and BFS were found to be 5%, 20% and 20% respectively, with a desirability of 0.942. Under these conditions, the MDD and CBR values were found to be 1450 kg/m3 and 28.60% respectively. The improved characteristics due to the combined application of additives in the soil render suitability of the RSM method in quantifying the stabilizer dosage.Keywords: Contaminated soil, immobilization, stabilization, optimization, strength parameters.