An analytical discussion of a theoretical model of Fingero‐imbibition in a cracked porous medium, of small inclination, is presented in this paper. The phenomenon is assumed to occur in a double‐phase displacement process involving two immiscible liquids of small viscosity difference in which the injection is initiated by imbibition and the consequential displacement of the relatively more viscous native liquid produces fingers. The nonlinear differential system governing this phenomenon is mathematically formulated and an approximate solution, using a perturbation technique, has been obtained.