It is easy to distinguish between males and females. Males are smaller, with thick tails and reddish-brown eyes. Female European turtles are larger, with shorter tails and mostly yellow eyes.

In warmer regions, female European sea turtles can produce three litters per year Eggs, each nest can lay 5-10 eggs, which are very prolific turtles; but in colder regions, European swamp turtles usually breed only once every 2-3 years.