This study investigated whether combining melatonin and apoptotic adipose-derived mesenchymal stem cells (A-ADMSC) was superior to ADMSC alone in ameliorating sepsis-induced acute lung injury. Adult male Sprague-Dawley rats (n=50) were randomized equally into five groups: sham controls (SC), sepsis induced by cecal-ligation and puncture (CLP), CLP-melatonin, CLP-A-ADMSC, and CLP-melatonin-A-ADMSC. Circulating interleukin (IL)-6 at 6, 18, and 72 hrs, were highest in CLP and lowest in SC groups, higher in CLP-melatonin than CLP-A-ADMSC and CLP-melatonin-A-ADMSC groups, higher in CLP-A-ADMSC than CLP-melatonin-A-ADMSC groups (all p<0.001). Immune reactivity (indicated by circulating cytotoxic-, and regulatory-T cells) and WBC count at 72 h exhibited the same pattern as that of circulating IL-6 (all p<0.001). Changes in histological scoring of lung parenchyma and the number of CD68+ and CD14+ cells showed a similar pattern compared to that of IL-6 level in all groups (all p<0.001). Changes in protein expressions of inflammatory (oxidative stress, RANTES, TNF-α, NF-κB, MMP-9, MIP-1, IL-1β), apoptotic (cleaved caspase 3 and PARP, mitochondrial Bax), fibrotic (Smad3, TGF-β) markers and those of reactive-oxygen-species (NOX-1, NOX-2) displayed an identical pattern compared to that of circulating IL-6 in all groups (all p<0.001). Anti-oxidative capacities (GR+, GPx+, HO-1, NQO-1+) and angiogenesis marker (CXCR4+ cells) were lowest in SC group but highest in CLP-melatonin-A-ADMSC group, lower in CLP than CLP-melatonin and CLP-A-ADMSC groups, and lower in CLP-melatonin than CLP-A-ADMSC groups (all p<0.001). In conclusion, combined melatonin and A-ADMSC were superior to A-ADMSC alone in protecting the lung from sepsis-induced injury.