This paper is an attempt to detail the dualism observed in the cosmology of both the Cham monuments and contemporary Cham society. It first outlines the dualistic cults as represented in two royal sanctuaries, My Son in the north and Po Nagar Nha Trang in the south of the Champa kingdom. The My Son sanctuary was located in a deep valley surrounded by high mountain ranges and it was here that the god Bhadresvara/father/ mountain/areca were worshipped. On the other hand, the Po Nagar Nha Trang Sanctuary was located on a riverside hill near an estuary where the goddess Bhagavati/ Po Yang Inu Nagar/mother/sea/coconut were worshipped. Similar to the dualism observed in these two key sanctuaries of Champa, we can also observe cosmological dualism within contemporary Cham communities along the south central coast of Vietnam. The Cham people of this region are divided into two groups based on their religions. One group, called the Cham or Ba-la-mon (Brahmanists) are adherents of an indigenized form of Hinduism; the other group called Bani, are adherents of an indigenized form of Islam. The paper details the cosmological dualism within these communities. The study concludes by suggesting that cosmological dualism is a key concept for understanding Champa, elucidating both the structure of the kingdom in the past as well as the structure of contemporary Cham society.