ABSTRACT This article aims to define the main facets and challenges of undocumented migrants on the move in Fez city (Morocco) and their impact on neighbourhoods and on society at large. It seeks to measure the integration of sub-Saharan migrants in the host community through the metrics of their participation in economic and social activities in urban space and discusses the main hurdles impeding their integration. The data show that there is, on the one hand, a quite low degree of acceptance by the local population, which in general tolerates their presence although signs of discrimination and prejudice in certain neighbourhoods are observed. On the other hand, the sample shows that some sort of partial integration occurs through forms of micro-entrepreneurial activities and use of city services. Further, the article proposes the idea of rethinking the concept of citizenship in order to understand the new flows of migration. It shows that the concept of citizenship needs to be re-considered beyond the formal and legal dimension, in order to include informal dimensions for a more realistic rendering of the interaction between migrants and the city. Unlike Isin (2017. “Performative Citizenship.” In The Oxford Handbook of Citizenship, edited by Ayelet Shachar, Rainer Bauböck, Irene Bloemraad, and Maarten Vink, 500–523. Oxford: Oxford University Press) and others who focus mainly on acts of citizenship as political, the article reveals that migrants perform their own acts of citizenship through social interaction, in line with Ong's (2007) theory of mutations of citizenship.