The prediction of the temperature profile inside an operating electric motor is one of the most important challenges while designing a motor and its associated cooling & lubrication system. This paper describes an integrated thermal simulation methodology for a surface mounted permanent magnet (SMPM) synchronous motor by coupling 1D thermal network analysis with 3D thermal simulation. 1D lumped parameter model is developed with a network of interconnected nodes and thermal resistances representing the heat processes within the SPMSM. The resistances are calculated using theoretical formulae and this thermal network is presented as a system of linear equations solved using matrix operations. Further this network is integrated with 3D FEM model in which lumped parameters are replaced by physical parameters to observe temperature variation within different motor components and simulated in 3D through commercially available tool. Both 1D and 3D simulated results show good agreement with each other as well as available experimental results.