It is found in west Asia, in Iran and central Turkey, northward to the Republic of Georgia, eastward to southwestern Turkmenistan, and in Iraq, Saudi Arabia, and Bahrain.

A pair of low lateral keels are present on the pleural scutes of hatchlings, but these become lower with age and disappear completely in adults.

Females are generally larger than males, have flat plastra and shorter tails with the vent under the rim of the carapace.

[4][5] The nominate subspecies occurs in central Turkey and northern Iran, northward to the Republic of Georgia and eastward to southwestern Turkmenistan.

It has wider reticulations on its carapace than M. c. rivulata, and a yellow-to-tan plastron with a regularly shaped, large, dark blotch on each scute.

Siebenrock's Caspian turtle (M. c. siebenrocki )[6] occurs in Iran and Iraq, with relict populations in Saudi Arabia and on the island of Bahrain; it intergrades with M. c. caspica in Mesopotamia.

This light form with contrasting colors resembles M. c. caspica, but has a yellow-to-orange plastron with a small to medium-sized, regularly shaped dark blotch on each scute.

[5] The spotted-bellied Caspian turtle (M. c. ventrimaculata)[4] is endemic to the highlands of the Kor and Maharloo basins in southern Iran.

It is distinguished from the M. c. caspica and M. c. siebenrocki subspecies by a yellow plastron with one or several irregularly shaped black spots on each scute.

The western Caspian turtle, formerly M. c. rivulata[7] and now recognized as its own species Mauremys rivulata, ranges throughout southeastern Europe (former Yugoslavia to Greece, the Ionian Islands, Crete, and Cyprus), Bulgaria, eastern to south-central Turkey, coastal Syria, Lebanon, and Israel; records from the vicinity of Ankara and from Lake Emir are questioned by Fritz.

[5] Its plastral formula usually is abd > fem > pect > gul > an > hum in both sexes, but variations of this have been described in İzmir populations.

Rivulata and members of the main caspica group are known to produce (presumably fertile) hybrids, so they should never be housed together in captivity[10] The Spanish pond turtle (Mauremys leprosa) was formerly considered a subspecies of M. caspica, but studies of the electrophoretic properties of its proteins,[11] and studies of its morphology[12] have shown it to be a separate species.