This study reports a new hybrid integrated technique to predict the absorptivity of absorber and the interface temperature of the joint in laser transmission welding. The new approach is more robust as the numerical model is confirmed through experimental observations initially with weld width and further with surface temperature. Experiments are performed on a polycarbonate sheets with electrolytic iron powder (EIP) as an absorber. The surface temperature and weld width are measured from the experiments. A transient 3-D finite element-based numerical model is developed for heat transfer analysis. The variation of heat flux with stand-off distance is also considered to enhance the accuracy of the computed results. The absorptivity is tuned in the numerical model so that the numerical weld width is in close conjunction with the experimental weld width. The numerical model is validated by comparing the upper surface temperatures at the center, measured in the experiments using infrared thermography. The results indicate that the surface temperatures in the numerical model are in good agreement with experimental observations, and the average error is less than 6%. The interface temperatures are estimated after the validation of the numerical model.