This study theoretically investigates the effect of adding nanofillers on the mechanical behavior and relative water flux of reverse osmosis (RO) membranes used in seawater desalination. The Halpin–Tsai model was used to estimate the effective elastic modulus of nanofiller-reinforced membranes as a function of filler type, volume fraction, and shape factor. Three nanofillers were considered: graphene oxide (GO), silicon dioxide (SiO₂), and titanium dioxide (TiO₂). The calculated elastic modulus was then linked to membrane compressibility and relative water flux under different operating pressures. The results indicate that nanofiller incorporation improves membrane stiffness and reduces pressure-induced deformation. GO showed the highest predicted reinforcement effect, followed by TiO₂ and SiO₂. .............. Keywords: .................Nanofillers; Reverse osmosis; Halpin–Tsai model; Relative water flux; Membrane compaction; Desalination.