The present work deals with the co-current imbibition phenomenon which occurs when two immiscible phases oil and water flow through an inclined heterogeneous porous medium. The solution to the governing equation, which is a nonlinear partial differential equation, is obtained in the form of an infinite series using Reduced Differential Transform Method (RDTM) [1]. By solving this equation, we can determine the saturation of injected water in a double phase flow at various distances and time. Additionally, the impact of inclination on water saturation is analysed. MATLAB is utilized to obtain the numerical solution and graphical representations.