This paper presents results on the impact of Laser CO2 process variables on the weldability, phase transformations and tensile properties of a TRIP800 Steel. The microstructure of this steel is comprised of ferrite, bainite and retained austenite phases. This is obtained by controlled cooling from the intercritical annealing temperature to the isothermal bainitic holding temperature. These steels have been increasingly used in the last 10 years in the automotive industry and for these materials to be used effectively; the influence of material and the CO2 laser welding process condition must be clearly understood. Hence, in this work the effect of the welding process on the resultant microstructures and on the exhibited mechanical properties is investigated. It is found that the tensile strength of welded specimens falls below 800 MPa and that the elongation becomes 15 % or lower. In turn, this clearly indicates that the implemented laser welding process leads to a reduction in the TRIP800 steel toughness.