Seed dispersal plays a pivotal role in plant ecology, impacting various aspects such as dispersal, reproduction, and population dynamics. In this study, we investigated the endozoochoric seed dispersal by the onager or Persian wild ass (Equus hemionus onager) in Qatrouiyeh National Park, located in south-central Iran. Fecal samples were collected from three plains within the park over three seed production seasons. A subsequent greenhouse experiment was conducted to identify and quantify the germinated seedlings. We discovered a total of 63 plant species across 45 genera and 21 families, with the majority of species categorized as annual or perennial forbs. Seasonal variations were observed for seedling count, species richness, and species diversity, with peak values observed during autumn. The seedlings consisted primarily of forbs (86%), followed by grasses (10%) and other plant types (4%). Astragalus podolobus, Lepidium vesicarium, and Chenopodium album emerged as the most abundant species from the fecal samples. Our findings shed light on the critical role played by the onager in the dispersal of numerous plant species and emphasized the potential cascading effects of herbivore-mediated seed dispersal. This highlights the significance of conserving and restoring the remaining populations of this threatened subspecies in arid habitats, where seed dispersal by abiotic factors is limited.