The waste of coal mining activities causes accumulation of hazardous elements in soil for plants. Biochar is considered an important soil remediation strategy to stabilize the heavy metals. The aim of this study was to quantify the effect of biochar sources and rate on the heavy metal stabilization in coal-contaminated soil. Biochars of three feedstocks (maize straw (MBC), rice straw (RBC), and sugarcane bagasse (SBC)) with four levels (0%, 0.5%, 1%, and 2%, i.e., 0, 10, 20, and 40 ton ha⁻¹) were applied to two types of soils (naturally contaminated soil (NCS) versus artificially contaminated soil (ACS) spiked with Cd, Cu, Cr, and Pb). Plastic pots were incubated at 30% field capacity for 90 days at 25 °C, and soil pH, electrical conductivity (EC), and heavy metals concentration were measured after 1, 4, 8, and 12 weeks. Among the biochars, RBC showed maximum immobilization of Cd, Pb, Cu, and Cr as compared with MBC and SBC. Similarly, biochar application increased heavy immobilization, being maximum at 2% (40 ton ha⁻¹) rate compared with control. The pH of both soils with biochar addition increased as compared with control. The remediation effect of biochar on heavy metal stabilization was positive over time. The higher rate (40 ton ha⁻¹) of RBC for ACS and MBC for NCS could be used effectively for heavy metal stabilization.