Formaldehyde is one of the most common difficult-to-eliminate indoor air pollutants. Among the available methods of eliminating formaldehyde, adsorption is still the most commonly used due to its simplicity, efficiency, and economic viability. This study investigated the potential of diatomaceous earth (DE) adsorbent for formaldehyde (low concentration in air). DE was considered because of its high silica content and high porosity. It also examined the effect of adding ethylene-diamine (EDA) on the adsorption performance of DE. Amine groups have been proven to improve the adsorption of formaldehyde through their reaction that produces imine. The amount of added EDA was varied from 0.25 to 0.75 g per gram of DE. For pure DE adsorbent, the adsorption performance was 298 mg/g. Adding 0.75 g of EDA resulted in maximum DE adsorption performance (565 mg/g). EDA-modified DE was shown to be a potential adsorbent for removing formaldehyde in air.