📓 Schistosomiasis caused by Schistosoma (S.) mansoni is one of the major public health problems in the world including Egypt. Immunodiagnostic methods are more applicable for their better sensitivity and specificity than other methods. The detection of leucine aminopeptidase (LAP) in serum could be more valuable in diagnosis; hence early treatment could be applied before irreversible damage takes place. S. mansoni LAP antigen was purified from excretory/secretory (ES) products by DEAE-ion exchange chromatography and was injected into rabbits to raise specific polyclonal antibodies (pAb) which was used as a primary capture to coat ELISA plates. The secondary capture pAb was prepared by conjugation of primary pAb with horse-raddish peroxidase (HRP). Sandwich-ELISA was performed for S. mansoni infected mice and Egyptian patients' serum samples and showed sensitivity of 89.29% and 85%, respectively, and specificity of 88.89% and 80%, respectively in comparison to those infected with other parasites and control. The data of this study, denotes that sandwich ELISA technique appears to be a sufficiently sensitive assay for the detection of schistosomiasis. In addition, LAP detection in the