The name 'Mordvin', or also 'Mordva', appears for the first time in written sources in some of the works of Jordanes, a Gothic historian, from the 6th century as he mentions the existence of a tribe called 'Mordens'. In the De Administrando Imperio (written from 948 to 952) of Eastern Roman Emperor Constantine VII, it is mentioned that a region called 'Mordia' is located about 10 days' journey from the territory of the Pechenegs (a Turkic people groups who lived on the Russian steppes from the 9th to 10th century).

Further on, in the early Middle Ages, the neigbours of the Mordvins included the, now extinct and unclassified within Uralic, Meshchera and Muroma peoples to the north and northwest, the Mari to the northeast, the Turkic Bulgars to the east and the Judeo-Turkic Khazars to the south. The latter two both established long lasting empires, respectively Volga-Bulgaria (7th-8th century to 1236) and the Khazar Khaganate (650 to 969). The Khazars whould then later on be replaced by the Pechenegs (see above). From the 12th century on, the Mordvins are frequently mentioned in Russian chronicles. The Kievan chronicle, for example, states that Yaroslav Svyatoslavich, prince of the principalities of Murom and Chernigov, fought the Mordvins in 1103 but was defeated.

The foundation of the Nizhniy Novgorod in 1221, then only a wooden fortress and one of the eastern most Slavic strongholds, was an important step in the Russian colonisation and presence in the area. In the years after its foundation, the fortress was attacked multiple times by Mordvin forces. By then, the Erzya and Moksha had started to developed seperatly, and from the 13th century onwards, an irreconcilable war between them existed. The Erzyan prince, Purgaz (Пургаз) allied with the Volga-Bulgarians in an attempt to stop the advancing influence of Kievan Rus' while Puresh (Пуреш), the Mokshan prince, collaborated with the principalities of Kievan Rus'. Following the Mongol invasion in 1237 Puresh became an ally of the Mongols, accompanying him to battle in 1241 in Legnica, Poland, where he and many other Moksha were eventually killed after secretly negotiating with Henry II the Pious. In 1253, a troop of Moksha even reached Germany. The Erzyans, on the other hand, had helped the Volga-Bulgarians ambushing and forcing the Mongols to retreat at the battle of Samara Bend a few years earlier, in 1223.