During the 17th century, the Jesuits focused their mission on evangelizing frontier territories that had not yet been Christianized. Their foundations were primarily based on an ideology that sought to convert indigenous peoples, while also promoting the protection of their culture. The case of Bolivia is evidenced by six missions located in the eastern region bordering Brazil, declared World Heritage Sites by UNESCO, which present a fusion of the compositional principles of the Baroque developed in Europe, but mimicked with features of indigenous culture. This syncretism is recognized as mestizo Baroque. The objective of this study was to identify the religious and compositional guidelines that shaped the earliest constructions at urban, architectural, and aesthetic scales, and to evaluate their persistence through the appropriations and interpretations made by local inhabitants. To achieve this, the historical method was first employed to understand the initial intentions behind this architecture, followed by the descriptive method to identify the elements that reflect all or part of its Baroque heritage. The study determined that this Baroque fusion is present not only in the original mission towns but also in newer communities that replicate these characteristics on a smaller scale.