The ametryne herbicide is largely used on sugar cane plantation in Brazil. It is persistent in the environment and can be found in bodies of water, impacting the aquatic and terrestrial ecosystems. Generally, in crops are applied mixtures of herbicides in order to obtain a higher success in combating weeds. This study evaluated the toxicity only of ametryne herbicide, without mixture with other herbicides, in order to quantify only the degree of dangerousness. This work evaluated the toxicity of ametryne to one aquatic test organism (Daphnia similis) and two land test organism (Eruca sativa and Lactuca sativa). Immobility of D. similis was evaluated in the presence of ametryne. Influences of ametryne on seed germination and root growth of E. sativa and L. sativa were evaluated. Even at low concentrations (5.00 mg/L), ametryne caused toxic effects on the mobility of D. similis, and 0.25 g/L caused toxic effects on the seeds. Root growth and the percentage of inhibition showed greater sensitivity to ametryne compared with seed germination. Thus, ametryne resulted in toxic effects to the analyzed organisms, which may bring damage to both aquatic and terrestrial ecosystems.