High　concentrations　of　oil　and　salt　can　adversely　affect　the　effectiveness　of　anaerobic　membrane　bioreactors　(AnMBRs)　for　food　wastewater　treatment,　yet　the　impacts　of　their　co-occurrence　remain　unknown.　This　study　evaluated　the　performance　of　an　AnMBR　in　response　to　simultaneous　oil　and　salt　stressors　in　synthetic　food　wastewater,　in　terms　of　methane　production,　membrane　fouling,　and　microbial　activity.　Results　show　that　either　8　g/L　of　cooking　oil　or　9　g/L　NaCl　in　food　wastewater　caused　the　failure　of　AnMBR　operation　with　a　notable　reduction　in　methane　production　and　severe　membrane　fouling.　However,　the　co-occurrence　of　oil　and　salt　achieved　a　higher　methane　yield　compared　to　oil　stress　alone.　Additionally,　the　co-occurrence　of　oil　and　salt　could　alleviate　osmotic　stress　to　reduce　microbial　secretions　and　form　macromolecular　precipitates,　thereby　mitigating　membrane　fouling,　compared　to　oil　and　salt　alone.　Such　mitigation　was　due　to　the　co-occurrence　of　high　oil　and　salt　to　reduce　long-chain　fatty　acids,　enhancing　living　cells　and　their　electron　transfer　activity.　Further　microbial　analysis　evidenced　that　the　co-occurrence　of　oil　and　salt　enriched　hydrolytic　and　acidogenic　bacteria　(e.g.　Bacteroidetes,　Proteobacteria,　Thermotogae,　and　Synergistetes)　as　well　as　hydrogenotrophic　methanogens　(e.g.　Methanolinea)　to　upregulate　genes　related　to　methanogenesis　for　methane　production.　Furthermore,　key　enzymes　involved　in　the　hydrogenotrophic　methanogenesis　pathway　(M00567)　were　augmented　when　8　g/L　of　oil　was　simultaneously　added　with　9　g/L　of　salt.　©　2025