Paddy field is one of the major sources of methane to atmosphere. Bioturbation by aquatic earthworms can change soil surface environment in paddy field, thus it is expected to influence methane emission from paddy field soil. This research was conducted to determine the role of earthworms on methane flux from paddy field soil and to know the effects of farming practices on earthworm density in paddy field. In a laboratory study paddy field soil was incubated at 20^oC for 28 days with and without inoculation of Branchiura sowerbyi. In laboratory condition methane emission flux was increased by 72% on day-28 in comparison to day-7 with no inoculation of earthworms. Meanwhile opposite trend was observed with earthworm inoculation, where methane emission flux was decreased by 54% with the same time span. Cumulative methane flux was decreased by half in earthworm inoculated paddy field soil in comparison with no earthworm-inoculated soil. Tillage (conventional vs. no-tillage) and fertilizer (chemical vs. organic) were the factors in the field experiment. Both tillage and fertilizer practices had no significant effect on earthworm abundance in the paddy field soil during the field experiment. Activity of aquatic earthworms needs to be considered for mitigation of methane emission from paddy soils.