Phytochemical screening of the ethanolic extract of leaves of Cleome viscosa indicates the presence of glycosides, alkaloids, steroids and gums. Pharmacological interest of these compounds, coupled with the use of this plant in traditional medicine tends to investigate for possible cytotoxic and free radical scavenging activities. Traditionally this plant is used to relieve earache and the bruised leaves are applied to the skin as a counter-irritant. As it has a great antibacterial effect and antiviral effect, it must have some toxic effect to biological organ. Moreover, every toxic substance is a drug at lower doses. The ethanolic extract of leaves of Cleome viscosa showed significant lethality (cytotoxic activity) against the brine shrimp nauplii as well as free radical scavenging activity. The obtained results provide a support for the use of this plant in traditional medicine.