We analyzed the main factors that controlled the prey-predator dynamics of two invasive ctenophores, Mnemiopsis leidyi and Beroe ovata in the Black Sea using a demographic model. We assessed the bottom up cascading effect from edible zooplankton to its consumer M. leidyi and its predator B. ovata. For these purposes, we used life cycles of both ctenophores (ova, larva, juvenile, transitional and adult stages), variability of annual phenology and physiological features obtained from our field observations and experiments made in the northeastern Black Sea over 27 years, combined with a long-term change in temperature and food availability for both ctenophores. Model outputs were compared with field observations. Then, model scenarios were tested to understand which environmental conditions control M. leidyi and B. ovate development. Using our model, we found that the maximum annual abundances of M. leidyi and B. ovata increased with mean springtime temperature and development of spring-early summer zooplankton which is important for creation of M. leidyi abundance and consequently development of B. ovate. An assessment with changing concentration of the M. leidyi food (i.e. zooplankton) at the time of its annual development changed the maximum annual values reached by M. leidyi, and consequently B. ovate. It was found that time of appearance of B. ovata had changed to May since 2012 with increasing temperature, and as a result M. leidyi did not have time to reach high abundance, being grazed by B. ovate already since May. Model results were qualitatively the same as those from long-term field observations. As a result, we obtained a model of two ctenophores interacting with total life structure: duration and scale of reproduction, growing from stage to stage, mortality, seasonal disappearance from water depending on temperature and prey availability. Similar analyses have never been done in the Black Sea and can be used for other seas where M. leidyi or both ctenophores invaded.