In this work a computational model for the numerical simulation of multi-pass welding and metal deposition processes is presented. A fully coupled thermo-mechanical solution, including phase-change phenomena and shrinkage effects, has been considered. Temperature evolution, residual stresses and distortions due to the successive welding layers are accurately studied, coupling the heat transfer analysis with the mechanical field. The deposition of the material is simulated considering an ad-hoc activation methodology able to follow the welding path and, consequently, generating new elements. Special care has been devoted to the activation procedure both from the thermal and the mechanical points of view. The proposed model has been validated by comparing the numerical results with the experimental data, in terms of either the temperature history at different locations or the distortion of the welded part.