The gaseous mixed dimers NaDyBr4 and NaDyI4 and the bromo-iodide species DyBrI, DyBr2I, DyBrI2, NaDyBr3I, NaDyBr2I2, and NaDyBrI3 were generated in an effusion cell reactor at elevated temperatures using several different source configurations and were identified by mass spectrometry. A number of gaseous equilibria involving these species were studied, and thermochemical properties were derived with the aid of thermal functions based on estimated molecular constants. Enthalpies of formation of NaDyBr4 and NaDyI4 are compared with values in the literature, while results for the bromo-iodides are in close accord with values interpolated from data on the pure metal bromides and iodides.