Thirty-four levels in Tb158 have been observed up to an excitation energy of 1166 keV utilizing 12-MeV deuterons and the reaction Tb159(d,t)Tb158. The ground-state Q value was determined to be -1870 +/- 15 keV. The spectrum has been interpreted in terms of the coupling of the [411↑] Nilsson proton orbital with the neutron orbitals prominent in the (d,t) spectrum of Gd157. This interpretation has resulted in the determination of relative energies due to the residual neutron-proton interaction for eight different configurations. The observed singlet-triplet splitting energies for the [521↑], [402↓], and [400↑] neutron orbitals coupled to the [411↑] proton orbital were measured to be +132, -111, and +136 keV, respectively. Theoretical calculations of these energies made for a zero-range spin-dependent central potential gave values of +174, -186, and +136 keV, respectively.