The purpose of the thesis is to study the ritual practices of Kinh people’s Goddess worship in Nha Trang to clarify the relationship between efficaciousness and transformation of ritual practices. The thesis uses methods of analysis, information synthesis and qualitative research (observation observations and in-depth interviews). The dissertation addresses issues such as ritual forms of Goddess worship and their efficaciousness from aspects of performativity and practical strategies with new findings as follows: Identify ritual practices of Goddess worship in Nha Trang from the historical and cultural context as well as the acculturation of the Cham and the Kinh people; The acculturation is the basis to understand the Goddess worship in Nha Trang; Explore the transformation process from “attending a seance” to four Goddess worship that has derived from ritual practices and daily life ones. It is important to identify characteristics of the authority of ritual practices providing new arguments for analysis framework on ritual efficaciousness; The efficaciousness which has derived from performativity strategy and daily life present practitioners’ behaviors and their adaption to changes in the environment and livelihoods. This adaptation clearly demonstrates the subjectivity and authority of the practitioners.