The globalization process resulted from technological and economic developments in the second half of the 20th century has created a rapid urban transformation in the world and Turkey as a developing country. This rapid urban transformation has affected the urban and architectural context of cities, including Istanbul, both in negative and positive ways. Urban policies, which lay the groundwork for minimizing the negative effects of rapid urbanization on cities and producing more inclusive life scenarios, are mostly based on socio-cultural sustainability approaches. However, when urban policies are concerned, the issue of sustainability is usually approached from the perspectives of ecological and/or physical features, whereas the significance of socio-cultural sustainability for urban development strategies is often neglected. Within this framework, this study aims to examine the potentials and constraints that Mecidiyeköy encompasses as an “urban threshold” and to inquire the ways that socio-cultural sustainability can offer a ground for future urban policies and architectural practices to trigger the co-existence of differences and social interaction between them. This study is designed as a case-study and the methodological framework of the study consists of literature review and on-site observations. This article revealed that socio-cultural sustainability, as a conceptual framework and urban approach, can provide a fertile ground for future urban scenarios that would be developed for Mecidiyeköy. If approached from the socio-cultural sustainability perspective, it can be ensured that this region having constraints and potentials in terms of accommodating spatial and human diversity and triggering the interaction between them, can actually work as an “urban threshold.”