In this study, the reduction of lateral swelling pressure on retaining walls in expansive soils is investigated. Swelling pressures can develop if the soil is not allowed to swell freely. When some soil expansion is allowed, the swelling pressure may decrease considerably relative to conditions under which no expansion is allowed. This study introduces a new method for reducing the lateral swelling pressure on retaining walls by using the inclusion of soilbags. A modeling experiment was conducted to examine the roles of the inclusion of soilbags in accommodating soil expansion and reducing the lateral swelling pressure on adjacent retaining walls. Two artificial rainfall events were created during one month of monitoring. The results showed that the inclusion of soilbags were more permeable and enhanced drainage, which shortened the duration of the delayed response to lateral swelling pressure and kept the lateral swelling pressure steady when it reached its peak value during the rainfall period. The soil expansion was restricted in the bags during rainfall infiltration, which resulted in a reduction in the swelling potential of the soilbags. The lateral compressibility of the wetted soilbags was relatively high, which allowed for lateral expansion of the soil, especially under a small vertical load. These findings indicate that the lateral swelling pressure can be effectively reduced by using the inclusion of soilbags