Paddy field is a major source of methane (CH₄) emission. Farming practices like fertilization and tillage are important for proper growth of rice plants. Feeding activities of aquatic earthworms in paddy soil add oxygen in upper soil layers by introducing oxygen rich water. Therefore, field and pot experiments were conducted to identify effects of agro-chemicals and tillage on CH₄ emission and earthworm density and role of aquatic earthworms on reduction of CH₄ emission. During field experiments, soil samples were collected under fertilizer (organic and chemical) and tillage (conventional and no-tillage) treatments to measure earthworm density and gas samples were collected to measure CH₄ flux. In pot experiments, urea, ammonium sulfate and aquatic earthworms (Branchiura sowerbyi) were imposed in soil in combination. In the field experiment, organic fertilizers enhanced earthworm density and no-tillage farming practice reduced CH₄ emission. In the pot experiment, ammonium sulfate directly reduced CH₄ emission and the aquatic earthworms were found to have significant effect on suppression of CH₄ emission from paddy soil. While the application of urea increased CH₄ emission, earthworm reduced CH₄ flux under urea fertilization condition. Results of these studies revealed that aquatic earthworms may play important role to reduce CH₄ emission from paddy field.