Abstract: Background and objective: Cryptosporidiosis is a common gastrointestinal disorder in humans and animals caused by various Cryptosporidium species. At present, many antiparasitic drugs have been tested but only a few have been shown to be partially effective in treating cryptosporidiosis. Therefore, the aim of this study was to evaluate the ability of some essential oils and their major compounds (MCs) to destroy both species of Cryptosporidium: C. baileyi and C. galli. Materials and methods: A screening of the oocysticidal activity of five EOs and three MCs was carried using the direct contact method in a liquid medium. The release of substances absorbing at 273 nm was measured after treatment of Cryptosporidium oocysts with thymol and carvacrol. Results: Among the EOs tested those of thyme, oregano and clove as well as their MCs; thymol, carvacrol and eugenol were the most effective, with low LC50 (<0.4 mg mL–1). The release of substances absorbing at 273 nm after treatment of Cryptosporidium oocysts with thymol and carvacrol show that the treatment of oocysts with these components led to their lysis in a dose and time-dependent manner. Conclusion: We were able to conclude that these EOs and their MCs are of particular interest in fighting cryptosporidiosis since they have a destructive effect on oocysts at very low concentrations. They could also help in the formulation of radical and safe solutions to cryptosporidiosis.