Dynamic filtration equipped with a perforated disk was adopted for the first time to dewater and concentrate Tetraselmis suecica, from a typical solution of 2–100 g/L of dense biomass suited for the downstream process. An ultrafiltration membrane, polyethersulfone 150 kDa, was found to best perform in terms of high biomass retention and filtration rate. At 1600 rpm, the highest rotation speed of the disk we tested, plateau permeate flux increased up to 20.2 times higher than those with no rotation; this improvement was attributed to fouling reduction (up to 98%) via distinctively high-shear stress on the membrane surface. Even at a high biomass concentration (100 g/L) where fouling formation was very serious, the heightened shear stress caused high flux to be maintained and fouling resistance to be reduced in an effective way. When trans-membrane pressure was increased in a stepwise manner, flux continuously rose at high rotation speed; at low speed, on the other hand, the limiting flux was observed. The dynamic filtration with the perforated disk, which was an effective high-shear stress generator, was proven to be a promising dewatering means of T. suecica, and especially so for the production of highly concentrated biomass.