Three new hafnium aluminum antimonides Hf5Al3- xSbx (x = 0.70, 1.44, 2.14) were synthesized from pure elements in an arc-melting reaction; structures were solved from the X-ray diffraction data of single crystals. Al and Sb mixing produced two homogeneity ranges; the Mn5Si3 structural type was homogeneous for 0 ≤x ≤ 1.0, and the W5Si3 structure covered the range 2.0 ≤x ≤2.5. Both structures are condensations of two polyhedrons stacked along the c-axis. Calculations of the electronic structures revealed substantial contributions from Hf-Sb interactions; heteroatomic bonding in Hf-Al and Hf-Sb contacts affected the stabilities of these two phases. Measurements of the resistivity of polycrystalline samples revealed a dependence on temperature, indicating metallic behavior, consistent with the results of our calculations.