In this work, a fully coupled thermo-mechanical meshfree approach is developed for the first time to simulate a solid-state layer-by-layer additive manufacturing process, Additive Friction Stir-Deposition (AFS-D). The meshfree method in this present work uses a Lagrangian reference frame, which permits tracking of material point history. A solid mechanics formulation is used, allowing the resolution of both elastic and plastic strains. An explicit dynamics time stepping scheme is used to ensure that the code is robust for the large level of non-linearity native to the AFS-D process. In this present work, a description of the meshfree method will first be described. Then a new thermo-mechanical joining contact algorithm will be introduced. Following that, a description of the experimental setup for the AFS-D model calibration experimental one layer deposition cases is explained. Subsequently, the simulation model and results for three different parameter sets will be detailed and compared against the experimental results. Finally, temperature and strain rate gradients are revealed across the entire deposition elucidating spatial-temporal flow phenomena in the AFS-D process. Display omitted •Additive Friction Stir-Deposition simulations reveal inherent temperature and strain rate gradients.•Computationally efficient novel meshfree formulation facilitated by General-Purpose Computing on Graphics Processing Units.•Smoothed particle hydrodynamics simulations correlated to physical depositions representing acceptable and poor builds.•Simulations elucidate role of heat input on varying amounts of frictional heat generation influencing material flow.