Researching ancient languages is notoriously difficult in sociolinguistics, due to the scarcity of data. This challenge is addressed by utilizing recent sociolinguistic theories and models to investigate the prestige languages used by early Christians in Acts. Drawing on historical documents, archaeology, and inscriptions, this study reconstructs the complex multilingual settings of the time. It reveals how Greek, despite the diverse linguistic landscape, became the dominant language in nearly all official contexts of early Christianity. This work breaks new ground in understanding early Christian communities and their linguistic practices, offering historical sociolinguistic approaches to the study of ancient languages and societies.