In the 9th century BC, Assyrians based in northern Iraq started a relentless process of expansion that within two centuries would see them controlling most of the ancient Near East. Traditional explanations for the decline of the Neo-Assyrian Empire in the 7th century BC have emphasized the role of military conflict, and especially the destruction of the Assyrian capital, Nineveh, by a coalition of Babylonian and Median forces in 612 BC. However, it remains unclear how the Assyrian state, the most powerful military machine of its age and the largest empire the Old World had ever seen up to that time, declined so quickly. In this paper, we highlight two potential factors which may have had some influence upon the Assyrian decline that have not been previously explored. The first is a major increase in the population of the Assyrian heartland area at the dawn of the 7th century BC, which substantially reduced the drought resilience of the region. The second factor is an episode of severe drought affecting large portions of the Near East during the mid-7th century BC. We propose a series of testable hypotheses which detail how the combination of these two factors may have contributed to the development of considerable economic and political instability within the Assyrian Empire, and argue that these demographic and climatic factors played a significant role in its demise.