The aim of this article is to describe the impact of secularization processes in Poland on the transformation of symbolic religious boundaries in small local communities, as well as to offer an in-depth scholarly reflection on the mechanisms and consequences of these changes. The analysis focuses on a specific region in the eastern borderland, characterised by a high level of religious and ethnic diversity and a low level of urbanisation, which limits the influence of secularization processes. To verify the hypotheses, an analysis was conducted on research material obtained from semi-structured qualitative interviews with young, educated residents of Podlasie who grew up in villages and small towns but currently live in Białystok. The collected material revealed that respondents experienced a significant decline in religiosity, which began during adolescence and had a crucial impact on the redefinition of symbolic religious boundaries between believers and non-believers in their traditional hometowns. While the distinction between Orthodox Christians and Catholics was accepted, atheists often faced exclusion or social isolation.