The objective of this paper is to study the effect of institutional factors on investment and economic growth of a set of 11 countries in the MENA region during the period 2000-2009, using a model of dynamic panel data. The effect of institutions on the contribution of investment to economic growth has been a second empirical study in this paper. The key findings generated by these two empirical tests stipulate a significant relationship between institutional variables and investment on the one hand and economic growth on the other hand, a positive interaction between political institutions and investment and a negative interaction between political instability and investment.