The paper presents the results of finite element study conducted by developing a three dimensional model of single cylinder engine piston assembly. A new method to estimate the piston assembly friction by finite element approach on the bases of IMEP (Indicated Mean Effective Pressure) without using any instrumentation and engine modification has been discussed. The basic CAD model of the engine cylinder required to build finite element model was developed using Ug-Nx-3 software. The finite element model of the single cylinder engine cylinder piston assembly was generated by using HYPERMESH 7 preprocessing software. The respective boundary conditions, loads, material properties, contact pairs were defined to mimic the real working conditions of the engine. In order to impose the effect of lubrication one dimensional Reynolds equation was solved to find hydrodynamic pressure acting on the piston skirt. The final model is solved by L.S.Dyna solver. The results of finite element simulation were used to calculate the piston assembly friction force. The forces required to calculate the piston assembly friction force by IMEP method were obtained from finite element simulation. The results obtained are compared with earlier reported experimental studies. It is concluded that the finite element approach can be used as an inexpensive tool to estimate the piston assembly force in the beginning stages of engine design and where the experimentation are difficult.