The peace treaty of 674 BC between Elam and Assyria is a unique treaty in the history of relations between these two states since this treaty is the only friendly treaty that one can speak of it with certainty. The context of this treaty has not left, but there are references to it in Assyrian letters, prophecies and royal inscriptions that can affirm its existence. The reasons for its conclusion and violation have not been examined before and since this treaty shows a clear turning point in the policies of two sides, we will survey these reasons in this research. In studying this treaty, we have no Elamite evidence, so our emphasis is on the Mesopotamian sources. According to these sources, in the seventh century BC, Iranian plateau by the arrival of Scythians and Cimmerians and rise to power of Iranian peoples who entered the plateau before this time, experienced dramatic changes. The coalitions between peoples who were residing in the plateau, especially Iranian people and these newcomers against Assyrian expansionist policies in addition to threatening eastern borders of the Assyrian territory, put northern borders of Elam in danger. Furthermore, Elam had troubles with Persians in its eastern regions. So Elam and Assyria, who were exposed to a common enemy, by concluding this treaty became allies. Nevertheless, this treaty was violated in 664 BC by Elam’ s attack on the Assyrian territory. Causes such as lack of complete adherence to the treaty from both parties, factionalism among the ruling class in Elam, shared economic interests between Elam and southern Mesopotamia, and resentment against the Assyrian control over these regions that put their economic interests in jeopardy, will be examined as what prepared the setting for violating the peace treaty.