This qualitative study examines the neighborhood effects on the economic mobility of the inhabitants of three segregated neighborhoods in Salvador (Brazil), in other words the socio-economic advantages and disadvantages affecting the lifes of poor people due to their embeddedness in specific socio-residential contexts. According to the hypothesis of social isolation, the missing articulation with social networks and institutions representing mainstream society and the insufficient exposition to middle class role models foster the reproduction of poverty. However, major disagreement remains whether the contiguity between residents of poor neighborhoods and higherclass condominio-dwellers provides structures of opportunities. Based on a survey analyzing the inhabitants’ egocentric networks, the study confirms that the proximity of Nordeste de Amaralina to middle-/upper-class communities improves the access to labour opportunities. Nevertheless, mechanisms of social segmentation annihilate these potentials. The residents´ networks reveal a high degree of homophily and localism. Segregational structures and the scarcity of economic opportunities in Plataforma foster the networks’ fragmentation whereas the social heterogeneity of Fazenda Grande II interviewees and the socialising effects of public institutions mitigate the impact of segregation. The networks’ composition admits a greater proportion of bridging ties. The study concludes emphasizing the relevance of the social isolation hypothesis in Urban Sociology whenever the process of social network building operates in contexts of segregation where social space appears to be highly congruent with the geographical environment. Whereas Nordeste de Amaralina and Plataforma risk to become socially isolated, the Fazenda Grande II case demonstrates that public investments in social infrastructure stimulate interclass interactions.