A significant barrier for wide-spread use of continuous carbon fiber reinforced plastics based on thermoplastic matrix materials (TPC) is the lack of economic, quick and reliable component manufacture processes, especially joining steps. In this article, a new approach for the laser transmission welding of unreinforced and short glass fiber reinforced PA 6.6 to continuous carbon fiber reinforced PA 6.6 is presented. It is shown that it is mainly the carbon fiber fabric within the thermoplastic composite material that determines the heat conduction and therefore influences the heat transfer from the laser absorbing to the laser transparent joining partner, resulting in an inhomogeneous weld seam formation. By introducing an on-line pyrometer-based process control, it is possible to minimize the influence of the carbon fiber reinforcement by realizing a constant process temperature within the center of the welding trace, resulting in a shift of the achieved weld seam strength curve to lower line energies. An additional paint layer, based on carbon black particles, on top the composite material, increases the absorptivity for the laser wavelength, which results in an increase of the achievable seam strengths in case of temperature controlled laser transmission welding