In this study, the extraction of europium from nitric acid solution by a flat sheet supported liquid membrane using Cyanex272 as a carrier was investigated. The influence of effective parameters on the extraction of Eu was studied and the optimum conditions were derived. Then a theoretical model was developed for unsteady-state transport of Eu ions through the supported liquid membrane. In this model, the variation of carrier concentration in the membrane phase was taken into account. The partial and complete differential equations obtained for the feed, membrane, and stripping phases were numerically solved and the results were compared with the experimental data. The verified model was used to simulate the concentration distribution of the metal-carrier complex and carrier as a function of position and time in the membrane phase. Using the results of numerical solution, the derived equations were also solved analytically.