This article presents an analysis of the architecture of the Church of the Conversion of St Paul the Apostle in Kraków, one of the significant examples of early modern sacred architecture in Poland. The aim of the study is a comprehensive examination of the church’s architectural form through a detailed description of its structure, formal analysis, genetic interpretation, and comparative analysis, as well as an attempt to address the problem of the building’s authorship. The research demonstrates that the church of the Missionaries in the Stradom district is deeply rooted in the tradition of post-Tridentine Roman sacred architecture, drawing inspiration from solutions developed in Baroque churches in Rome, while at the same time creatively adapting these models to local spatial and functional conditions. The motivation for undertaking this research lies in the need for a more in-depth examination of the church’s architecture, which has so far been discussed primarily within the broader context of its artistic history, and in highlighting its original character and importance for the development of early modern sacred architecture in Kraków.