European common spadefoot toad, Pelobates fuscus, is the only representative species of Pelobatidae family in Croatia. Despite the species is widespread all over the Europe, there are many data concerning the global population is in decline. According to the Red List of Amphibians and Reptiles of Croatia, common spadefoot toad is categorized as DD (data deficient). It inhabits lowland areas and flatlands near slow moving or stagnant waterbodies with little or no predator and loose soil (natural or anthropogenic habitats). Researched area includes stagnant waterbody in the village Lijeva Luka, Sisak – Moslavina Country. There were two egg clutches found and kept under controlled conditions with the aims of: 1) detailed morphological description of tadpoles and their oral disc through developmental stages, 2) the existence of morphological adaptations of P. fuscus and R. temporaria in the competition experiment, 3) the existence of morphological adaptations of P. fuscus in the presence of predator fish Umbra krameri. Tadpoles were treated equally and sampled in 3 % formaldehyde. Tadpoles were scanned and measured using the ImageJ programme and digital caliper. Developmental stages from 23 to 41 were determined with the highest value of total body length of 99,04 mm. All morphological features of oral disc with accompanying formulas were illustrated and described in detail. Spadefoot toad tadpoles did not show significant morphological changes within the competition experiment.