Although the alien Red-eared slider (Trachemys scripta elegans) is generally argued as an invasive species that competes with native turtles, the ifeld evidence on its diet is controversial. Field studies conducted at the Gutian Nature Reserve of Guangdong and along the Wanquan River in Hainan, China show that T. s. elegans is an opportunitic omnivore, consuming a wide variety of food items. Consumption varies throughout its range;more plant material is consumed in Guangdong, compared to a more carnivorous diet in Hainan;and juveniles are also found to have a more carnivorous diet than adults. This implies a high adaptability to new environment. Sympatric native Mauremys sinensis shows a more herbivorous diet and a narrower niche breadth (0.0260) in Hainan, plus a low niche overlap (0.3048) with T. s. elegans, providing a potential empty niche for the invasive T. s. elegans. Red-eared slider is also known to consume large quantities of native prey species to disrupt the ecological balance. It is imperative to understand the invasive nature of this species and the mechanisms by which it affects native ecology.