When Buddhism was first brought from China to the Korean Peninsula in 372 CE, Shamanism was the indigenous religion. Shamanism is the ancient religion of animism and nature-spirit worship and its origins in Korea are lost in antiquity. It is based on the belief that human beings as well as natural forces and inanimate objects all possess spirits or that they are gods. Since Buddhism was not seen to be in conflict with the rites of nature worship, it was able to naturally blend in with Shamanism. And so many of the special mountains believed to be the residences of gods in pre-Buddhist times, soon became the sites of Buddhist temples.

Korean Shamanism regarded three gods with special reverence and importance: the Mountain God, Sanshin (who is usually depicted as an old man with a tiger at his feet), the Toksong, or recluse, and Ch'ilsong (the god of the seven stars, the Big Dipper). Buddhism accepted and absorbed these three gods and, even today, special shrines are set aside for them in most temples. The Mountain God, in particular, receives due veneration following the ceremonies honoring the Buddha in the Main Hall. And thus Chinese Buddhism blended with Korean Shamanism to produce a unique form: Korean Buddhism. As in other Buddhist countries, the fundamental teachings of the Buddha remained the same, even though the form, influenced by indigenous culture and customs, was uniquely Korean.