Activated carbon is a prominent adsorbent for removing hazardous chemicals, and abundant natural resources allow the production of activated carbon utilizing various sources of biomass. This study aims to investigate the capacity of carbon prepared from Coffea arabica grounds waste in adsorbing methanal. The carbon from used coffee grounds was activated using ZnCl2 30% in a microwave at 800 Watt for 10 minutes. The characteristics of activated carbon investigated include moisture content (1.47%), ash content (4.74%), and iodine number (803.7 mg/g). The study of methanal adsorption was carried out under the following conditions: adsorbent mass (gram) (0.5, 1, and 1.5), contact time (minute) (20, 50, and 80), methanal concentration (ppm) (5, 10, and 15), and pH (2, 5 and 8). The optimum conditions for adsorption were studied using a central composite design (CCD), and the data were analyzed using Minitab 16 software. The adsorption was optimally achieved at 1.50 grams of adsorbent, 58.18 minutes of contact time, 10.15 ppm of methanal concentration, and pH of 2. The percent of adsorption of methanal at optimum conditions was 54.31%. The adsorption of methanal by activated carbon from Coffea arabica ground waste fit best with the Freundlich isotherm model (R² = 0.9918), indicating multilayer adsorption