Abstract After alkali-catalyzed transesterification reaction for biodiesel production, the glycerol-rich phases have to be separated. These phases are traditionally separated by settling, requiring long residence time, especially when soaps and gels are formed. In this work, biodiesel, and glycerol rich phases separation was experimentally assessed using poly(ether sulfone) hollow fiber membranes (PES-HFM). Experimental data were obtained in a continuous bench scale system. The effect of pressure difference through the membrane (0–0.6 bar), feed composition and biodiesel-rich phase mass fraction (0–0.8) on permeability and permeate composition were studied. In addition, a mathematical model adopting the Hagen–Poiseuille transport equation for membrane ultrafiltration, where permeate fluxes and compositions depend on the Liquid–Liquid Equilibrium (LLE), was proposed, correlated and experimentally validated. Experimental results demonstrated only glycerol-rich phase permeated through the membrane following the LLE. Glycerol-rich phase flux increased when pressure difference through the membrane augmented, and decreased when permeate viscosity increased. The highest experimental permeability (33.2 kg bar−1h−1m−2) was obtained at the highest methanol content in the feed stream, 66%wt., equivalent to a molar ratio methanol to oil 18:1 fed to the reactor. The mathematical model predicts an increase in the glycerol-rich phase flux when temperature and methanol content augment. The transport mechanism coupled to the mathematical model explained accurately the membrane role in the separation of the compounds involved in transesterification of vegetable oils, as well as the membrane selectivity.