Syntheses and in vitro antimalarial evaluation of 42 new thioureidoquinazolines have been carried out. Several analogs showed promising antimalarial effect in the in vitro investigation against chloroquine-sensitive 3D7 strain of Plasmodium falciparum whereas one of the compounds shows 50% curative effect in the mouse model at an oral dose of 100 mg/kg × 4 days against multidrug resistant Plasmodium