This study aims to assess the effects of two pesticides, namely the insecticide carbofuran and the herbicide isoproturon, on monospecifically cultivated marine and freshwater phytoplankton according to standard methods. In the presence of pesticide, growth rates were lower in marine species Chaetoceros gracilis and Phaeodactylum tricornutum than in freshwater species Chlorella vulgaris and Selenastrum capricornutum after 72 hours. The EC50 values were obtained with the REGTOX Macro software, and the NEC values by applying the DEBtox model.