Sulvanites have the parent formula Cu₃MCh₄. The metal M belongs to group 5 and Ch is a chalcogen. The tantalum sulvanites Cu₃TaS₄ and Cu₃TaSe₄ are predicted to have wide band gaps and p-type conductivity and show promise in optoelectronic applications. Their potential as p-type transparent conductors or efficient photocatalysts for visible-light water splitting is a valuable incentive to explore these materials in their nanoscale form, toward bottom-up processing opportunities. Reported herein are the first syntheses of nanosized Cu₃TaS₄ and Cu₃TaSe₄ sulvanites, which preserve the parent cubic crystal structure but show that morphology at the nanoscale is dependent of the reaction conditions. The two solution-based methods for synthesizing the tantalum S and Se sulvanites result in Cu₃TaS₄ or Cu₃TaSe₄ nanocrystals (NCs) with prismatic morphology, or, in the case of Cu₃TaSe₄, could lead to core-shell spherical nanostructures. The Cu₃TaS₄ NCs and Cu₃TaSe₄ NCs have good absorption in the UV-Vis region, while the Cu₃TaSe₄ core-shell NCs possess broad absorption bands not only in the UV-Vis but also in the near-infrared region. Photoluminescence measurements of Cu₃TaS₄ and Cu₃TaSe₄ reveal optical bandgaps of 2.54 and 2.32 eV, respectively, consistent with the values measured in bulk. Additionally, the current–voltage (I-V) curve of Cu₃TaS₄ NCs proves its electrical conductivity.