Replacing the expensive Pt catalyst of counter electrodes (CEs) with a low-cost Pt-free catalyst has been regarded as one of the crucial steps for cost effectiveness of dye-sensitized solar cells (DSSCs). Herein, MnWO₄ as a binary mixed oxide (MnO–WO₃) has been prepared with (NH₄)₁₀H₂(W₂O₇)₆·xH₂O and Mn(NO₃)₂·4H₂O via a facile hydrothermal method. DSSCs using MnWO₄ CEs show power conversion efficiency (PCE) of 4.93%. To improve the catalytic activity of MnWO₄ CEs further, three proportions of MnWO₄@AC mixed oxide composite catalysts have been fabricated via simple physical mixing MnWO₄ with activated carbon (AC) by ball-milling. Moreover, the DSSCs with the MnWO₄@AC composites CEs generate high PCE of 6.50, 6.45 and 6.12%, respectively, from MnWO₄ : AC mass ratios of 1 : 2, 1 : 1 and 2 : 1 for the regeneration of traditional iodide/triiodide (I₃⁻/I⁻) redox couples, which were superior to the pristine MnWO₄, Pt- and AC-based counterpart 4.93%, 4.54% and 2.10% CEs under the same test conditions and method. The favorable performances make MnWO₄@AC composites act as a new resource of electro-catalytic Pt-free materials for high-performance CEs in the encapsulation of DSSCs.