The impact of the ERP (enterprise resource planning) on the company’s flexibility is at the center of a controversy. While some researchers emphasize the positive contribution of the ERP in terms of flexibility, others emphasize its rigid nature. This paper aims to validate the positive impact of ERP’s integration on the strategic flexibility of Tunisian firms. As this impact is not obviously strong and positive, we choose to introduce three moderating variables: the number of modules, the firm size and the period following the installation of the ERP. The empirical analysis shows that the ERP, measured by its integration capacity, has a positive impact only on reactive strategic flexibility. The findings also show that moderating variables have no effect on the relationship ERP/flexibility.