Abstract Previous phytochemical studies have shown that the plants of the Albizia genus (Fabaceae) contain bioactive saponins, lignans, spermine alkaloids, flavonoids, glycosides phenols and pyridoxine derivatives. Their extracts sometimes display medical properties, but can have also toxic effects. The purpose of our study was to determine the in vivo toxicity of Albizia bernieri seeds in the experimental model of the medaka fish embryo, which is recommended for use in toxicity studies. Our results show clearly that incubating the embryos or larvae of the medaka fish in a medium containing A. bernieri extracts caused a dose-dependent reduction in embryo or larvae survival. Embryos exposed to an extract of A. bernieri displayed cerebral lesions, such as cell lysis and the emergence of lysosomes in the glial tissue. We conclude that when comparing with data obtained with different plant extracts tested on medaka development in our laboratory, A. bernieri displays an unusually high toxicity. Focussing on the cerebral target as well as the fish behaviour could bring more specific informations.