古アッカド時代には、イナンナはアガデの都市に関連するアッカドの女神イシュタルと習合した<ref>Asher-Greve, Westenho, z, 2013, p62</ref>。 この時代の讃美歌には、アッカド人のイシュタルが、ウルクのイナンナ、ザバラムのイナンナと並んで「ウルマシュのイナンナ」と呼ばれているものがある<ref>Asher-Greve, Westenholz, 2013, p62</ref>。 イシュタル信仰とイナンナとの習合はサルゴンとその後継者によって奨励され<ref>Asher-Greve, Westenholz, 2013, p62</ref>、その結果イシュタルはメソポタミアのパンテオンの中で最も広く崇拝される神々の一つとなるに至った<ref>Leick, 1998, page87</ref>。サルゴン、ナラム-シン、シャル-カリ-シャリーの碑文では、イシュタルが最も頻繁に登場する神である<ref>Asher-Greve, Westenholz, 2013, p172</ref>。
古バビロニア時代には、前述のウルク、ザバラム、アガデのほか、イリプが主な信仰の中心地であった<ref>Asher-Greve, Westenholz, 2013, p79</ref>。
In the Old Babylonian period, her main cult centers were, in addition to aforementioned Uruk, Zabalam and Agade, also Ilip.{{sfn|Asher-Greve|Westenholz|2013|p=79}} Her cult was also introduced from Uruk to Kish.{{sfn|Asher-Greve|Westenholz|2013|p=21}}
During later times, while her cult in Uruk continued to flourish,{{sfn|Black|Green|1992|page=99}} Ishtar also became particularly worshipped in the [[Upper Mesopotamia]]n kingdom of [[Assyria]] (modern northern [[Iraq]], northeast [[Syria]] and southeast [[Turkey]]), especially in the cities of [[Nineveh]], [[Assur|Aššur]] and [[Erbil|Arbela]] (modern Erbil).{{sfn|Guirand|1968|page=58}} During the reign of the Assyrian king [[Assurbanipal]], Ishtar rose to become the most important and widely venerated deity in the Assyrian pantheon, surpassing even the Assyrian national god [[Ashur (god)|Ashur]].{{sfn|Black|Green|1992|page=99}} Votive objects found in her primary Assyrian temple indicate that she was a popular deity among women.{{sfn|Asher-Greve|Westenholz|2013|p=20}}