Antialgal activity of Zataria multiflora, Satureja khuzistanica and S. rechingeri were evaluated. These plant species are easily cultivable and their algicidal activity make them suitable candidate as biocontrol. This study aimed to identify effective algicidal compounds, practically new algicidal agents from essential oils of plants that could inhibit the growth of red tide microalgae. Prepared essential oils of Z. multiflora showed the highest algicidal activity (LC50 1.35 mg.mL-1). Algicidal activities of essential oils of all plants exhibited dose dependency. Results of the assays showed that the growth of Cochlodinium polykrikoides was strongly inhibited by using different concentrations of the plants essential oils.