Sodium chlorite (NaClO₂) is applied as a disinfectant for the sanitization of food and environmental surfaces. HClO₂ (pKa = 1.86) is believed to be the main species responsible for the antimicrobial effects, whereas NaClO₂ solution ([HClO₂] / [ClO₂^-] = 10^-5.64 at pH 7.5) shows only weak antimicrobial activity at neutral pH conditions. However, NaClO₂ solution at a neutral pH has the advantages of having very low reactivity to organic materials and high stability for long-term storage at around room temperature. In our previous screening of food additives, phytochemicals, and related compounds, we found that caffeine could strongly promote the antimicrobial effects of NaClO₂ solution at a neutral pH. Caffeine is a purine alkaloid found in nearly 100 plant species that has very weak antibacterial properties against many bacteria. In the present study, we evaluated the antimicrobial activity of NaClO₂ in combination with caffeine against Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans strains. We found that caffeine strongly potentiated the antimicrobial action of NaClO₂ in all four strains, indicating that this combination has potential as a disinfectant.