Ascariasis, a geohelminthes infection in humans caused by Ascaris lumbricoides and occasionally by A. suum, is recognized as an important parasitic infection among children in the worldwide. In Sri Lanka, many cases have been reported among people in congested areas around Kalaniya and estates in up country. Diagnosis of Ascariasis is currently based on detection of Ascaris eggs in faeces. This study describes the extraction of Ascaris lumbricoides larval antigen and development of ELISA based on this larval antigen to improve the sero diagnosis of human ascariasis. The Ascaris larval antigen was extracted using developed A.lubricoides eggs. The analysis of the larval antigen was performed by SDS-PAGE followed by Western Blotting. Determination of cross reaction of Toxocara canis IgG antibody with Ascaris lumbricoides larval Antigen was performed to assess the specificity of the extracted antigen. Results revealed cross reaction between Ascaris larval antigens and anti-Toxocara canis serum. The whole larval antigen cannot be used for ELISA because it leads to false positivity, due to cross reaction with other ascaroids species.