As a country with a long coastline and a thriving fishing industry, Vietnam has a substantial fleet of fishing vessels. However, the majority are small, wooden-shell vessels less than 24 meters in length with restricted operational ranges, whereas the desired number should be considerably larger. Fishing vessels are small medium-speed vessels. Therefore, fishing vessels need to have good stability and maneuverability to ensure the safety of the crews. Various methods have been studied and tried over the years for damping the roll motion of commercial vessels, including fishing vessels. Using bilge keels is a traditional technique and widely used for reducing the roll motion of ships. In this paper, the natural roll motion of ships in calm water is studied based on five fishing vessel models such as: model BK00 without bilge keel, model BK01 and BK02 with flat bar bilge keel as FB200x10 and FB250x10, model BK03 and model BK04 with holland profile bilge keel HP200x10 and HP250x10, respectively. For each model, the roll motion is examined at inclinations of 10 degrees and 30 degrees. Star-CCM+ software is used for simulation. Based on the obtained results, the effect of shape and size of the bilge keels are compared and discussed. Model BK04 demonstrates reduced roll motion than other models, but it also has increased resistance relative to them.