Abstract: This study focused on improving the cathode performance of Ba_0.6Sr_0.4Co_0.85Nb_0.15O_3−δ (BSCN)-based perovskite materials through molybdenum (Mo) doping. Pure BSCN and Mo-modified-BSCN—Ba_0.6Sr_0.4Co_0.85Nb_0.1Mo_0.05O_3−δ (BSCNM_0.05), Ba_0.6Sr_0.4Co_0.85Nb_0.05Mo_0.1O_3−δ (BSCNM_0.1), and Ba_0.6Sr_0.4Co_0.85Mo_0.15O_3−δ (BSCM)—with Mo doping contents of 5mol%, 10mol%, and 15mol%, respectively, were successfully prepared using the sol–gel method. The effects of Mo doping on the crystal structure, conductivity, thermal expansion coefficient, oxygen reduction reaction (ORR) activity, and electrochemical performance were systematically evaluated using X-ray diffraction analysis, thermally induced characterization, electrochemical impedance spectroscopy, and single-cell performance tests. The results revealed that Mo doping could improve the conductivity of the materials, suppress their thermal expansion effects, and significantly improve the electrochemical performance. Surface chemical state analysis using X-ray photoelectron spectroscopy revealed that 5mol% Mo doping could facilitate a high adsorbed oxygen concentration, leading to enhanced ORR activity in the materials. Density functional theory calculations confirmed that Mo doping promoted the ORR activity in the materials. At an operating temperature of 600°C, the BSCNM_0.05 cathode material exhibited significantly enhanced electrochemical impedance characteristics, with a reduced area specific resistance of 0.048 Ω·cm², which was lower than that of the undoped BSCN matrix material by 32.39%. At the same operating temperature, an anode-supported single cell using a BSCNM_0.05 cathode achieved a peak power density of 1477 mW·cm⁻², which was 30.71%, 56.30%, and 171.50% higher than those of BSCN, BSCNM_0.1, and BSCM, respectively. The improved ORR activity and electrochemical performance of BSCNM_0.05 indicate that it can be used as a cathode material in low-temperature solid oxide fuel cells.