While it is quite common in studies of diversity to focus on its negative aspects, this paper specifically aims to emphasize the contribution of immigrants to the urban economic performance. By exploring different kinds of social integration, this paper discusses how immigrant groups can be important agents of urban economic growth and competitiveness by liberating creative forces and enhancing the competitiveness. Immigrant entrepreneurship is defined as the most important means of social inclusion and sustained economic performance in two different cities, with different features yet hosting considerable number of immigrants with diverse characteristics, namely Antwerp (Belgium) and Izmir (Turkey). The findings of our two case studies reveal that different kinds of diversity play an important role in urban economic performance. Immigrants contribute to the growth of different forms of production and services, not only because of their talents and skills, but also because of their social connections. Social capital enables immigrants to survive in a recipient country, and integrate into an economy as active agents. They can fill the gaps in an economy as entrepreneurs or the skilled labour, which are the most important assets for the cities aiming sustained economic growth in volatile economic conditions.