Activated carbon (AC) with high surface area and narrow pore size distribution was prepared from extracted Larix gmelinii (Rupr.) sawdust by alkaline activation through physical mixing. The preparation method has been optimized through the analysis of diverse experimental variables. Among them, type of activating agent and activating agent/sawdust ratio, activation temperature, and precarbonization have been studied. N₂ adsorption isotherm and scanning electron microscopy were used to determine the BET surface area, pore structure, and surface morphology. It was shown that chemical activation with KOH can be successfully used to develop an AC with a high surface area from extracted L. gmelinii sawdust. When the raw sawdust was precarbonized at 500°C for 1 hour, physically mixed with KOH (mass ratio of KOH/sawdust, 4:1), and activated at 750°C for 2 hours, an AC with narrow pore size distribution, a maximum surface area of 2,659.4 m²/g, and a total pore volume of 1.21 cm³/g could be obtained. Hg(II) adsorption capacity of AC produced under optimal conditions was 318.47 mg/g, much higher than the compared commercial adsorption value. With a high surface area, narrow pore size distribution, and large Hg(II) adsorption capacity, the AC prepared from extracted sawdust waste appears as a very promising adsorbent for pollution control.