This dissertation seeks to shed light on the broad range of practices that Vietnamese Buddhism has contributed to the American religious landscape since its arrival due to the impact of the Vietnam War. Despite the presence of almost one million Buddhist Vietnamese and their Buddhist temples and centers, flourishing in nearly in every state of America, the diversity of this Buddhist tradition, however, has largely been neglected in the current academic study of religion. The major practices, religious activities, adaptations, as well as obstacles faced by the tradition are still issues to be addressed. My dissertation, being grounded in an immigrantís experience and perspective, is intended to fill that gap, adding a more balanced and detailed view to the study of Vietnamese Buddhism. My historical, ethnographic, and phenmenological methods of study will establish the presence of major Vietnamese Buddhist practices, illuminating their contributions to American life, showing their adaptation and impact, and projecting the future prospect of the tradition. This dissertation, essentially, is a case study of religious adaptation and assimilation. I, however, do not limit my analysis to the theory that religious adaptation is promulgated merely by indigenous Buddhist cultural elites who have embraced and advocated the foreign faith in their own terms. Instead, I will add that religious adaptation is also initiated by the immigrants. The Vietnamese immigrants themselves, though trying to retain their Vietnamese Buddhist heritage, have initiated adaptation in order to serve the cultural and spiritual needs of their community in America. Adaptation is a survival mechanism for the immigrant communities.