Black cotton soil (BCS) is a problematic soil commonly found in many regions. The poor engineering properties make it unsuitable for construction purposes. In many ground improvement projects, BCS is routinely stabilized with ordinary Portland cement (OPC) and lime additives. These conventional stabilizers are manufactured using energy-intensive methods that produce significant CO2 emissions. In this study, Coal gangue (CG) was used to stabilize the BCS to compete with traditional stabilizers. This study aimed to assess the impact of CG on the plasticity and compaction properties of BCS. Atterberg limit, Free swell index, and compaction test were performed on CG-treated BCS with various proportions of 10%, 20%, and 30% of dry weight BCS. The results disclosed that the plasticity index of BCS is decreased as the dosage of CG increases. The free swell index of black cotton soil has been significantly reduced with an increase in CG content. Also, the Optimum moisture content (OMC) and maximum dry density (MDD) are obtained at 20% CG. Therefore, the study suggests that the usage of CG is an effective way to improve the geotechnical properties of BCS and make it suitable for construction purposes.