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Besides economic factors affecting economic growth, some cultural, political and social factors influence economic growth and development too; inter alia, social components play important roles. Social instability originating from social threats is one of the most important social components, which affects economic growth. This study aims to investigate the consequences of social instability on economic growth in Iran during 1981-2011. For this purpose, the Auto- Regressive Distributed LagModel (ARDL) and Error Correction Model (ECM) are estimated by Eviews.5 and Microfit 4.1. Using Principal Component Analysis (PCA), an index for social instability (absence of social capital) is made. The results show that physical capital, labor and social instability have the highest effectiveness on economic growth, respectively. Paying attention of policymakers to improving social conditions and reducing social instabilities may lead to higher economic growth.