Social networks have mostly been hailed by academic scholarship for their cohesive function in the context of migration. Drawing from ethnographic material collected during fieldwork in Istanbul between 2007 and 2009, this article sheds light on Nigerian migrants' experiences of informal social networks in the Turkish metropolis. The dominant position of social networks based on nationality in the arrival stage of transit is highlighted, and light is shed on mechanisms leading to cohesion as well as mechanisms leading to distrust.