Slightly acidic electrolyzed water (SAEW) has proven to be an efficient and novel sanitizer in food and agriculture field. This study assessed the efficacy of SAEW (30 mg/L) at 40 °C on the inactivation of foodborne pathogens and detachment of multi-resistant Staphylococcus aureus (MRSA) biofilm. Furthermore, the underlying mechanism of MRSA biofilm under heated SAEW at 40 °C treatment on metabolic profiles was investigated. The results showed that the heated SAEW at 40 °C significantly effectively against foodborne pathogens of 1.96–7.56 (lg (CFU/g)) reduction in pork, chicken, spinach, and lettuce. The heated SAEW at 40 °C treatment significantly reduced MRSA biofilm cells by 2.41 (lg (CFU/cm2)). The synergistic effect of SAEW treatment showed intense anti-biofilm activity in decreasing cell density and impairing biofilm cell membranes. Global metabolic response of MRSA biofilms, treated by SAEW at 40 °C, revealed the alterations of intracellular metabolites, including amino acids, organic acid, fatty acid, and lipid. Moreover, signaling pathways involved in amino acid metabolism, energy metabolism, nucleotide synthesis, carbohydrate metabolites, and lipid biosynthesis were functionally disrupted by the SAEW at 40 °C treatment. As per our knowledge, this is the first research to uncover the potential mechanism of heated SAEW treatment against MRSA biofilm on food contact surface.