<p>Thermal conductivity of contaminated soil is a key thermal parameter for pollution investigation, soil remediation efficiency by thermal treatment. In this study, the thermal conductivity of contaminated soil was experimentally measured using the thermal probe method. The results demonstrated an increase in thermal conductivity with diesel content, which was identified as a key influencing factor. The primary mechanism is that higher diesel content displaces air within the soil pores, leading to enhanced overall thermal conductivity. The effect of dry density on thermal conductivity is mainly caused by two mechanisms: the air in pores is displaced by non-aqueous phase liquids (NAPLs) and contact area increases as dry density increases. The effect of soil texture on the thermal conductivity cannot be ignored when the porosity is less than 0.5, especially for soil with high quartz content. Furthermore, the three models were evaluated, and the Cote model was identified as the most suitable for predicting the thermal conductivity of contaminated soils. To further enhance its performance, key parameters in the formulas for <i>k</i>_dry​, <i>k</i>_sat(N)​, and <i>k</i>_e within the Cote model were calibrated. After modification, the values of root mean squared error (RMSE) decreased from 0.091 to 0.026, indicating a significant improvement in predictive accuracy. The modified Cote model is applicable for predicting the thermal conductivity of NAPL-contaminated soils, covering both coarse-grained and fine-grained textures.</p>