Abstract: This study demonstrates that various systems of foreign astrology, originating in India, Iran and the Hellenistic world, played a significant, albeit hitherto largely unrecognized role, in the development of Buddhism during the Tang dynasty, which subsequently deeply influenced religious traditions across East Asia for several centuries. Although Indian astrology was made available in China from the fourth to seventh centuries, it was never widely implemented in China in these centuries, for it was only in the eighth century with the introduction of Mantrayna that Chinese Buddhists came to have a pressing need to observe astrology. This subsequently sparked popular interest in foreign astrology among Buddhist and non-Buddhist communities in China, a development that fostered the simultaneous development of astral magic comprised of elements from multiple sources, including some traced back to Greco-Egyptian and Near Eastern traditions. Around the turn of the ninth century, translation of astrological materials shifted from Indian to Iranian sources as a result of Persian astronomers operating at the court. The popularity of astrology additionally facilitated the proliferation of uniquely Chinese astral deities in Chinese Buddhism, most notably Tejaprabh Buddha and the seven stars of the Big Dipper. This understudied interaction that resulted from deep interest in astrology marks a significant transmission of cultural and religious knowledge through multiple civilizations.