The electronic structure and molecular properties of triply charged transition metal helides, HeTM³⁺ (where TM = Sc–Cu), have been investigated employing CCSD(T), MCSCF and MRCI methods. Dissociation energies and harmonic vibrational frequencies have also been determined. For all the triply charged helides, the ground state is dominated by the 3dⁿ electronic configuration. In addition, states with configurations that have holes in the metal 3dσ orbital exhibit greater binding energies. The suitability of single-reference methods and diagnostics for this series has been investigated, with the MCSCF wave function being the most reliable diagnostic tool for the applicability of SCF methods.