Band structure and Fermi surfaces of the A3B compounds V3Co, V3Rh, V3Ir and V3Os are calculated in FP-LAPW calculations. From V3Co to the V3Os compound one observes a decrease of the overlap for d-states from both V and B atoms; the center of gravity of the d-band for V moves upwards, while for the B-atom it moves toward lower energies. Hence, despite the band widening, a weakening of interactions takes place throughout this series, which leads to a lattice expansion as experimentally observed. The bonding mechanism in these compounds is found to be dominated by the lower energy d-states. Comparatively, the DOS at EF does not change appreciably between these compounds, except for V3Os, where a sharp peak is observed at EF. This feature leads to the highest electronic heat-capacity coefficient γ (2.31 \(\frac{\rm mJ}{\rm g-at K^2}\)) in this compound, which otherwise possesses the smallest Bulk modulus (209.05 GPa). In V3Os, for whom no report has been found, a stronger admixture between p-states from both metals near EF is observed, and the Os d-states form a common d-band with the V d-states between 0.4–0.6 Ry. A stronger s–s hybridization is observed for V3Co, which is in the source of the fact that this compound has an anomalously large quadrupole interaction and exhibits a positive Knight shift.