In this study indicators of agglomeration economies and their effect on entrepreneurship in the ICT industry are analysed in diverse urban contexts. Agglomeration economies have a stronger impact on new firm formation than on the growth of incumbent firms. Concentration and diversity both have a positive effect on new firm formation as well as on the growth of incumbent firms, while competition only has a positive effect on new firm formation. It is especially the effects of industrial diversity that are revealed to be sensitive to urban contexts: positive effects on new firm formation are attached to the connected cities and to the highly urbanized Randstad, and positive effects on firm growth to the intermediate zone, the connected cities and urban municipalities