New methods for estimation of surface tension and viscosity of pure component organic chemicals are presented. The Surface tension is estimated at 298 K while the viscosity is estimated at 300 K. For both properties, the combined group contribution-atom connectivity index approach has been employed, where the same set of experimental data is used for a group contribution (GC)-based model and all atom connectivity index (Cl)-based method and then the model parameters for the atorn-Cl method are used to predict the missing parameters of the GC method. In this way, using the same set of experimental data, the application range of the GC method is enlarged through the combined GC-Cl method. Group contributions for surface tension (98, 39. and 8 for first, second, and third order groups. respectively) and for viscosity (108. 39, and 12 for first, second, and third order groups, respectively) have been regressed using two collected sets of experimental data consisting of 420 compounds for surface tension and 445 for viscosity, including C, H, N, O, F, Cl. Br, and S atoms, some of which are complex polycyclic compounds. The new methods have been compared with other GC methods, and their use in mixture property models have also been highlighted through illustrative examples.