Surface tensions and thermal conductivities were measured for LiBr + 1,3-propanediol + water and LiBr + LiI + 1,3-propanediol + water. These two mixtures were chosen as one of the potential candidates for working fluids for absorption heat pumps. Surface tensions and thermal conductivities were measured by the capillary rise method equipped with a cathetometer and the transient hot wire method with a coated tantalum wire, respectively. The measured surface tension and thermal conductivity data were well correlated with a simple polynomial function of temperature and absorbent concentration. In addition, the surface tensions of LiBr + 1,3-propanediol + water containing a small amount of alcohol-based surfactants, n-octanol and 2-ethyl-1-hexanol, were also measured at 298.15 K by the ring method. An increase in the surfactant concentration up to about 500 ppm leads to a gradual decrease in the mixture surface tensions.