Ternary chalcostibite CuSbSe2 compound is known for low thermal conductivity. However, the poor electrical properties severely limit its thermoelectric performance. In this study, the Mn-doped CuSb1-xMnxSe2 (x = 0–0.04) samples were synthesized by vacuum melting with spark plasma sintering, and their thermoelectric properties were characterized. The results indicate that the impurity phase Cu3SbSe3 will be generated when Mn content x > 0.02, and the carrier concentration and mobility were optimized significantly for the Mn-doped compounds, thus enhancing the electrical transport performance. In terms of results, the PF increases from 1.3 × 102 to 2.18 × 102 µW m−1 K−2 at 673 K. Point defects and the second phase enhance phonon scattering and lead to a lower lattice thermal conductivity for CuSb1-xMnxSe2 compounds, the κl decreases from 0.39 to 0.26 W m−1 K−1 at 673 K. As a consequence, a maximum figure of merit ZT of ∼0.53 was achieved at 673 K for CuSb0.97Mn0.03Se2, which is 140 % higher than the intrinsic CuSbSe2.