In the first centuries after settling in present-day Bulgarian lands, the Slavs and Bulgarians were pagans. They worshipped many gods, major and minor—including the sky, the stars, natural objects, stones, and animals—and bowed down to idols.

The Slavs believed in one main god, Perun—the creator of lightning—to whom they sacrificed oxen and other animals. Other gods associated with the Bulgarian Slavs included Veles (patron of herds) and Svarog (patron of the hearth and blacksmiths). They also worshipped rivers and nymphs.

The Bulgars' supreme god was Tangra, the sky god. They developed a cult around certain animals—horses, dogs, red deer, and roe deer. Shamans and priests served as intermediaries, sending messages to the "other world." A tile from Madara probably depicts a shaman performing ritual activities. Official religious ceremonies took place in specially built kapishta (pagan temples of the Bulgarians).

People wore amulets to protect themselves from evil. The famous bronze rosette from Pliska likely served this protective function. It has seven rays covered with engraved symbols that probably formed an inscription—perhaps part of a spell used in magical rituals and divination.

In 864, during Prince Boris's reign, the Bulgarian people underwent a mass conversion to Christianity. The khan, his family, the boyars, and the people all renounced their former gods. This conversion aimed to unite the various tribes and ethnic groups by eliminating differences in religious practices. Christianity strengthened the state's authority and influence. Churches and monasteries were built throughout the country, becoming centers of spiritual life and education in the centuries that followed.