In recent years the OEM’s trend is to develop, especially for Diesel engines, smaller engines with higher specific power outputs to comply with both even more stringent emission requirements and vehicle performance. This leads to higher mechanical and thermal load on all engine components, so it is of fundamental importance to analyze these loads. This thesis work, developed at Punch Torino S.p.a., is focused on the steady-state thermal analysis for Diesel engine pistons, that is the first step of the whole piston design validation process. In particular, the aim was to use results coming from CFD3D analysis as thermal boundary conditions for the FEM simulation to obtain more realistic temperature distributions.