In recent years, there is a strong interest to sequester uranium from seawater as a sustainable source of nuclear fuel. In this work, ethylene glycol methacrylate phosphate-grafted membrane adsorbers were synthesized using UV-initiated free-radical polymerization. The synthesized membranes were evaluated in DI water and synthetic seawater at different pH values in both batch and continuous modes of operation. A maximum capacity of 15.3 mg of U (g of the membrane)(-1) was observed in synthetic seawater at pH 4.08. The membrane capacity was dependent on pH, swelling of the polymer network, and the ionic strength of the solution. During filtration, membranes with a lower degree of grafting recovered more uranium than membranes with a higher degree of grafting for a given feed condition. This work explores design considerations associated with the use of polymer-grafted membrane adsorbers to sequester uranium from seawater.