This thesis investigates the impact of formal and informal institutional constraints and social capital aspects on the economic performance of privatised firms in Tunisia. Also, this study underlines the role of the institutional constraints in the Tunisian business environment that may create two categories of firms, insiders and outsiders, which face unequal business opportunities and uneven associated transaction costs. There has been little empirical work that explores whether institutional constraints and social capital aspects affect the performance of the firms after privatisation. In addition, very few studies have tested the insider-outsider phenomenon. In fact, a very limited number of studies have considered investigating such issues in the region of the Middle East and North Africa (MENA). This thesis seeks to fill these gaps by empirically investigating the real effect of the institutional constraints and the social capital aspects on the sales and investment growth of the privatised firms. This research is therefore focused on the relationship between formal, informal institutional constraints and social capital aspects and the performance of the privatised firms in Tunisia as well as the insider-outsider phenomenon in the Tunisian business environment.