In Europe, the species is an opportunistic inhabitant of freshwater habitats, generally in close proximity to human habitation and/or recreation centres. In its native range, this is an inhabitant of a wide variety of water bodies, and is most abundant in soft-bottomed shallow habitats with minimal flow, abundant access to sunlight and extensive vegetation. A dietary generalist, this species is mainly vegetarian at the adult stage whereas it is carnivorous during the first two years of life.

Trachemys scripta is omnivorous and consumes a wide variety of plant and animal matter. Juveniles and subadults tend to be more carnivorous, whereas adults, especially when very mature, tend to become almost exclusively vegetarian.

Within the European region, this species is only present as an introduced species (Speybroeck et al. 2020). All three subspecies are widely found as introduced populations in Europe. Feral populations of this species are widespread and often reach high population densities. In Italy, it is present almost throughout the whole national territory, and the same is true in France. There is a wide indication that this species is able to reproduce in many different regions of Europe, and that its distribution is wider than about 20 years ago. The species has been recorded from the following European countries: Netherlands, Portugal (widespread, especially in the south), Spain (widespread at low elevations), France (widespread, except in the north), Italy (scattered throughout the country), Slovenia (near Italian border region), Greece (Crete), Austria (Vienna region), Germany, southwestern Switzerland, Croatia, Bulgaria, Czechia, Poland, Latvia and probably others (Anon. 2015). The list of countries included in this assessment is unlikely to be complete.

Citizen science records (iNaturalist) suggest occurrence throughout western Europe and east to Ukraine, and European Russia (iNaturalist records added to the 'countries of occurrence' table but indicated as 'presence uncertain' pending confirmation).

Trachemys scripta is native to Mexico and the eastern and central United States of America (TTWG 2021). Introduced subpopulations have been reported from numerous parts of the world, including the United States (e.g., Arizona, California, Hawaiian Islands, northeastern states), Mexico, Guadeloupe, Türkiye, Israel, South Africa, Taiwan, Thailand, Cambodia, Indonesia, and Australia.

McKeown, Sean. A Field Guide to Reptiles and Amphibians in the Hawaiian Islands. Diamond Head Publishing Company, 1996