The crystal and electronic structures, and the thermodynamic properties of Ni6Si2B and Ni6Ge2B with the Fe2P-type structure have been investigated by means of first principles calculations. The enthalpy of formation at T = 0 K of the Ni6Si2B compound is −46.75 kJ/mol of atoms. The calculated structural parameters and internal parameters of the Ni6Si2B compound are in very good agreement with the experimental data. The ternary compound Ni6Ge2B with the Fe2P-type structure is found to be stable in the Ni-Ge-B system with an enthalpy of formation of −30.79 kJ/mol of atoms. The total electronic densities of states have been computed. First principles calculations have also allowed to show that the Co6Si2B and Pd6Si2B ternary compounds with the Fe2P-type structure are not stable.