Serpins constitute the largest family of peptidase inhibitors in plants, animals and microbes. Genomic studies of Drosophila melanogaster have indicated the presence of 29 genes encoding proteins with a putative serpin domain. Little is known about the developmental functions of these serpins in Drosophila. In this study, the possible roles of Spn-5 gene have been investigated. Two mutations of Spn-5 as well as UAS transgenic lines of Spn-5 wild type gene and RNAi were used to study some possible functions of Spn-5 during Drosophila Development. Two lethal mutations of Spn-5 indicated their important function for larval viability, resulting lethal effect on the second instar larvae. To investigate the effects of these mutations on metamorphosis and adult flies both somatic and germ line clones systems were used. The obtained results showed high frequencies of melanotic tumors in both larval and adult stages, strong defect on bristles, wing and eye development as well as inhibition of oogenesis in homozygous clones. Over expression of UAS Spn-5 wild type using different specific GAL4 drivers showed dominant negative effect. Meanwhile, GAL4/UAS Spn-5 RNAi over expression showed efficient interference with the wild type gene expression during eye and wing development. In general, all resulted expressions were similar for those phenotypes in somatic clone assays. The obtained results indicated the importance of Spn-5 gene product(s) for proper development of wings, eyes, bristles and oogenesis as well as importance of this gene as negative regulator of Toll pathway.