Two new quaternary chalcogenides, Na₆CdSb₄S₁₀ and Na₃CdSbSe₄, were successfully synthesized by the high-temperature solid-state reaction in vacuum-sealed silica tubes. Note that Na₆CdSb₄S₁₀ crystallizes in the C2/c space group, whereas Na₃CdSbSe₄ crystallizes in the P2₁/c space group. As seen from their structures, Na₆CdSb₄S₁₀ exhibits a three-dimensional (3D) framework structure composed by the interconnection of isolated [(Cd/Sb)₂Sb₂S₁₀] clusters and two different layers formed by the NaSn (n = 4, 6) units; besides, the structure of Na₃CdSbSe₄ is composed of isolated _∞(Cd₃Sb₂Se₁₂)_n chains and 2D layers formed by the NaSe_n (n = 5, 6) units. Their optical performances (bandgap and Raman spectra) were also investigated. Moreover, theoretical calculation was used to analyze the structure–performance relationship of Na₃CdSbSe₄.