Inorganic contaminants, notably heavy metals, present a significant environmental threat, particularly when they are soluble and can be mobilized in the soil solution. Processes such as chemical washing, employing chelation, desorption, and solubilization can enhance the bioavailability of heavy metals, potentially leading to their leaching into groundwater and adjacent water bodies, thus disturbing ecological equilibrium. This study focuses on investigating the influence of biochar on the leaching behavior of heavy metals in soil. Controlled experiments were conducted using soil spiked with lead and cadmium nitrates, simulating real-world contamination scenarios. Sugarcane bagasse-derived biochar (SBB), pyrolyzed at 400 °C for 3 h, was utilized as an adsorbent to assess its retention capabilities. Various dosages of SBB (0, 1, 2, 5, and 10%) were added to the contaminated soil, which was then subjected to leaching by two strong acids, HCl and HNO3, at distinct pH values of 4 and 6. Results indicate that untreated soils exhibited higher levels of heavy metal leaching compared to biochar-treated soil. Regardless of biochar application rate, soils treated with HCl demonstrated reduced metal leaching. Moreover, higher dosages of biochar led to reduced cadmium removal in soils washed with both HCl and HNO3. Active functional groups including hydroxyl and carbonyl facilitated in reduction of metal species in the soil leachate. pH emerged as a significant factor influencing metal mobilization in the soil; lower pH values in washing agents like HCl and HNO3 resulted in elevated contaminant leaching levels, regardless of biochar dosage. This study underscores the effectiveness of biochar in mitigating heavy metal mobility in low-permeability soils.