This study explores the dual cation co-intercalation strategy to improve the electrochemical performance of rechargeable magnesium (Mg) batteries, which are hindered by the poor mobility of divalent Mg ions in cathode host materials. The strategy involves pairing Mg²⁺ with Li⁺ or Na⁺ in dual-salt electrolytes to exploit the faster mobility of the latter. Experiments and theoretical calculations detail the charge storage and redox mechanism of co-intercalating cationic charge carriers. Comparative evaluation reveals that the redox activity of Mg²⁺ can be significantly improved with the help of the dual cation co-intercalation strategy, although the ionic radius of the accompanying monovalent ion plays a critical role. Specifically, a higher Mg²⁺ quantity intercalates with Li⁺ than with Na⁺ in TiS₂ due to the absence of phase transition in the former case, enabling improved Mg²⁺ storage. The results highlight the dual cation co-intercalation strategy as an alternative approach to enhance the electrochemical performance of rechargeable Mg batteries, opening up new possibilities for advanced cathode materials in multivalent battery applications.This study explores the dual cation co-intercalation strategy to improve the electrochemical performance of rechargeable magnesium (Mg) batteries, which are hindered by the poor mobility of divalent Mg ions in cathode host materials. The strategy involves pairing Mg²⁺ with Li⁺ or Na⁺ in dual-salt electrolytes to exploit the faster mobility of the latter. Experiments and theoretical calculations detail the charge storage and redox mechanism of co-intercalating cationic charge carriers. Comparative evaluation reveals that the redox activity of Mg²⁺ can be significantly improved with the help of the dual cation co-intercalation strategy, although the ionic radius of the accompanying monovalent ion plays a critical role. Specifically, a higher Mg²⁺ quantity intercalates with Li⁺ than with Na⁺ in TiS₂ due to the absence of phase transition in the former case, enabling improved Mg²⁺ storage. The results highlight the dual cation co-intercalation strategy as an alternative approach to enhance the electrochemical performance of rechargeable Mg batteries, opening up new possibilities for advanced cathode materials in multivalent battery applications.