The detailed electronic structure of a layered semiconductor 1T-TiS₂ and its modification in Ni-intercalated Ni_1/3TiS₂ were studied beyond the full surface Brillouin zone by use of a momentum microscope and He-I light source on their in-situ cleaved surfaces. Clear dispersions associated with the electron Fermi surface (FS) pockets induced by the self-intercalated Ti in non-doped 1T-TiS₂ around the M points, as well as the hole FS pocket induced by the surface Ni in Ni_1/3TiS₂ around the Γ point, were confirmed in the observed high-resolution EB(k_x, k_y) band cross sections. A bird"s eye view of the two-dimensional band dispersions EB(k_x, k_y) clarified many complex band dispersions. The experimental results are compared with first-principles band calculations performed for the bulk as well as the one monolayer (ML)-TiS₂ and surface-1ML-Ni_1/3TiS₂. The characteristic changes of the band dispersions near the Fermi level (E_F) are ascribed to the contribution of the 3d states of the surface Ni atoms with the C_3v symmetry in contrast to the "D_3d" symmetry of the intercalated Ni. The importance of experimental studies of band dispersions in the full Brillouin zone is demonstrated, showing the high potential of momentum microscopy.