Early attempts by Parthian rulers to take Babylon were short-lived, but in 141 BC they established their kingship by celebrating the New Year festival. Chronicles and astronomical diaries continued to be written. An independent ruler of Maysan in the Sealand, Hyspaosines, captured the port on the Tigris, took control of Bahrain and Failaka to control Gulf trade, and briefly claimed kingship of Babylon. He wrote in Aramaic. The Parthians regained control and rebuilt the Greek theatre. The old buildings and city plan continued to be in use, although the Summer Palace had been reroofed with terracotta tiles. New kinds of text were written on clay in cuneiform, astronomical science developed; an archive shows that temples were still active, and much older literature was still prized. Greek knowledge of the Epic of Creation was still alive in Athens from the time of Alexander until the sixth century AD. The cult of Bēl had spread west to Palmyra, to the Aegean island of Kos, and north to Edessa. In AD 116 Trajan visited the Summer Palace on a pilgrimage to the place where Alexander had died.

The First Dynasty, an unbroken succession of Amorite kings, lasted 300 years despite a major rebellion. Babylon had close relationships with the nearby cities Sippar, Kish, and Borsippa. Trade and alliances reached much further. The Sumerian king-lists of earlier times were replaced by Babylonian equivalents, various cities having their own version. Kings briefly recorded major events; names were given to each year of their reign for dating documents. Trade was widespread, by canal and river, or overland by donkey. Royal edicts excluded certain groups from trade. Evidence comes from a profusion of clay tablets. Official letters are plentiful. Priestesses of Marduk carried out trade for Babylon in other cities. The temple of Marduk was built and furnished with a golden throne. Elamite control over several major cities, which left its mark on temple design, was ended by Hammurabi late in his reign; there is a possible connection with Genesis 14:1–16. Regular edicts were issued to release individuals from debt and to regulate trade. The main powers were Halab (Aleppo), Eshnunna, and Larsa, until Hammurabi achieved supremacy and claimed divinity. His successor Samsu-iluna followed his father’s example.