Ammonia (NH3) emitted from swine manure contributes to odor problems and environmental pollution in intensive livestock systems. Plant extracts containing natural saponins, such as Yucca schidigera (YS) and Quillaja saponaria (QS), are used as potential agents to reduce gaseous emissions. This study evaluated the effect of a YS–QS powdered extract on NH3 emissions from pig manure under controlled laboratory conditions. Nine cylindrical pots (23 cm diameter, 25 cm height) were filled with 5 kg of fresh pig manure and assigned to three treatments with three replicates each: untreated manure (T0), manure plus 250 mg/kg extract (T250), and manure plus 2,500 mg/kg extract (T2500). Pots were maintained at 30°C in insulated containers. The extract consisted of a commercially available YS–QS powder. Initial manure properties were pH 8.19 and oxidation-reduction potential –60 mV. Headspace NH3 concentrations were continuously measured using a multi-channel laser-based gas analyzer at ~67-second intervals. Based on the results, NH3 concentrations at day 0 for T0, T250, and T2500 were 35.31±11.07, 62.03±24.30, and 84.65±21.11 ppb, respectively. By day 2, the concentrations decreased to 29.40±12.69, 41.59±18.92, and 50.40±18.81 ppb. The overall reduction rates from day 0 to day 2 were 17% (T0), 33% (T250), and 40% (T2500), with T250 achieving approximately twice the reduction observed in T0. In conclusion, the YS–QS extract reduced NH3 emissions from pig manure, with treatments ≥250 mg/kg showing greater effectiveness than the untreated manure. These results support the potential use of plant-based additives to improve NH3 emission control in manure.