Abstract. Aim. The aim of study was to investigate morphological changes after the effect of magnetic fields on the embryonic development of Rana macrocnemis. Methods. We conducted four different experiments in which embryos at different developmental stages were exposed to the magnetic field. After hatching, the larvae were measured for the following morphological characteristics: trunk length, tail length, body length, tail height at base. Hypermagnetic conditions were created by increasing the tension of the natural magnetic field. The Petri dish with the egg mass  was placed at an equal distance (9 cm) between opposite poles of two permanent magnets of cylindrical shape. The north magnetic pole was on top and the south at the bottom of the cup. With this arrangement of the magnets, the magnitude of the magnetic flux was 11.5 m/T. Results. The body length is the most stable feature of all investigated species. The most variable parameter is the length of the tail. In the fourth experiment, under the influence of magnetic fields from the neurula stage to the tailbud stage, we observed the most pronounced decrease of features of tadpoles as compared with the control and with the other experiments. Conclusions. Thus, under the effect of hypermagnetic field at various stages of embryonic development of the Iranian long-legged wood frog, the linear sizes all diagnosed features of tadpoles in the test groups decreased, especially the length of the body and tail.