The mitochondrial antioxidant manganese superoxide dismutase (Mn-SOD) plays a vital role in defence against reactive oxygen species (ROS) in eukaryotic mitochondria. This study was conducted to characterise SOD as an antioxidant gene from haemolymph of third larval instar of the flesh fly, Sarcophaga argyrostoma after challenging with hydrogen peroxide. Mn-SaSOD of S. argyrostoma has a single open reading frame (orf ) of 765 nucleotides that encode a polypeptide of 254 amino acids. Subsequent analyses of Mn-SOD gene sequences revealed that the identified Mn-SaSOD gene in this study shared homology with similar genes from other insect species. In addition, four manganese ion-binding sites (metalbinding sites) and Mn-Fe SOD signature were identified within the orf of Mn-SaSOD. One putative transcription factor-binding site (TATT) within the 5′-flanking region was predicted. This finding suggests that Mn-SaSOD might be involved in environmental stress responses and could be used in the production of novel antioxidants to compensate for the increasing demand of natural antioxidants instead of the chemical synthetic ones.