The presence of potentially toxic metals in water causes a strong impact on environment and human health. In this study, activated biochar was produced by using chemical oxidation method from wheat straw as natural adsorbent and was employed for heavy metals competitive remediation. The morphology, structure, and chemical properties of biochar before and after adsorption were characterized by FTIR, XRD, SEM and EDX mapping techniques. The competitive adsorption efficiency of adsorbent for divalent cadmium (Cd) and lead (Pb) from contaminated water was investigated by using wide range of several initial metal concentration, contact time and pH. Maximum adsorption of Cd(II) and Pb(II) was found in the pH range of 6–8. The adsorption capacity for Cd(II) and Pb(II) was 8.85 and 9.03 mg/g, respectively. Thermodynamics parameters and kinetic models were applied to adsorption data. The isotherm data followed Langmuir model, corresponding to monolayer adsorption of the two ions in the contaminated water. The kinetic data followed the pseudo 2nd order kinetics model, which authenticates the chemisorption nature. The thermodynamic study indicated that Cd adsorption is a spontaneous exothermic process while Pb adsorption is an endothermic process. Mineral precipitation, surface complexation, and cation-π interactions are the major remediation strategies for Cd(II) and Pb(II).