Rewilding is a conservation strategy used to restore ecosystems to previous states and can involve the reintroduction of large carnivores into areas from where they had been previously extirpated. Whilst rewilding has been important for ecosystem functioning, it can have negative implications for naïve prey that have had no exposure to the presence of large carnivores. Therefore, understanding prey responses to the reintroduction of predators is crucial for management and conservation. We assessed the effects of reintroduced cheetahs (Acinonyx jubatus) on the vigilance of two species of naïve prey: the steenbok (Raphicerus campestris) and the springbok (Antidorcas marsupialis). We hypothesized that both species would increase their vigilance behaviour post-cheetah reintroduction, but that the steenbok would demonstrate a greater response due to their smaller body size and more solitary nature. To test this, we compared the vigilance of both species before and after the reintroduction of cheetahs. Both species increased vigilance within one year post-cheetah reintroduction, but the steenbok demonstrated a much stronger response with a ˜70% increase in the percentage of time spent vigilant post-cheetah reintroduction. Springbok levels of vigilance were lower (˜50% increase), which we suggest is a function of body-size and/or grouping behaviour. Importantly, we show that naïve prey species are able to exhibit a rapid response to the reintroduction of large carnivores. However, the variation in responses highlights the importance of species-level monitoring after large carnivore reintroductions.