This article examines the dynamic aspects of the Buddha's Birthday festival as it was celebrated from 1928 to 1945 in colonial Korea. A joint Japanese and Korean Buddhist event sponsored by the state, it became the signature religious and state festival. Although much politicized, the festival was also a culmination of Buddhist efforts in Asia to respond to modernity, nationalism, colonialism, and Christian missions. Paralleling the reinvention of Christmas in the modern period, Buddhists reconfigured the Buddha's birthday as a symbol of their religious identity and power. The Buddha's Birthday festival should be understood in the context of increasing contact and exchange among Buddhists in the East and the West. The festival's prominence was the result of complex negotiation and collaboration between Korean and Japanese Buddhists who both hoped the festival would advance their overlapping visions of Buddhism. The festival was not so much an imposition of the colonizer on a native culture as it was a dynamic, creative feature of modern Korean Buddhism in the colonial context.