The article presents the results of effect of new synthesized 1,4-naphthoquinone amide derivatives (FO-1 and FO-2) on morphological changes in loach Misgurnus fossilis L. embryos at early stages of embryogenesis and in larvae treated with these amide derivatives used in 10-3–10-7 M concentration range. The amide derivatives used in 10-3–10-5 M concentrations showed the embryotoxic action, caused deceleration and abnormal development (blastomeres deformation, loss of contact with neighboring germ cells) and further lead to expressed morphological changes in loach larvae. Based on these data, it can be suggested that amide derivatives penetrate the perivitelline membrane of embryos and the plasma membrane of blastomeres. However, embryos and larvae loach cultivation of medium supplemented with amide derivatives in lower 10-6 and 10-7 M concentrations developed normally and hatching process matched up with development time in control. It was found that the presence of morpholine fragment in derivatives of 1,4-naphthoquinone caused more pronounced embryotoxicity comparing with derivatives containing piperidine group. Clarification of the mechanisms of the effect of these drugs on the embryonic cells requires further study.