Although the climate scientists of the IPCC and the UC posit that religion may be helpful in persuading world populations to adopt the sustainable lifestyles necessary to mitigating climate change, the academic literature does not necessarily support this contention. One exception seems to be the case of Taiwan where two humanistic Buddhist groups have influenced the majority of Buddhists on the island to adopt important aspects of sustainable lifestyles. This multi-sited ethnographic study uses participant observation with formal and informal interviews to research these two groups—the Buddhist Tzu Chi Foundation and Dharma Drum Mountain—in the two different social contexts of Taiwan and California. A comparative analysis of the results finds that the believers’ adoption of pro-environmental lifestyle changes is strongly influenced by their membership in a strong moral community, by sensing the material and social, or “terrestrial,” strain of environmental degradation coupled with a feeling that the government and other official institutions are not doing enough, and by integrated religious teachings, which include theory and praxis, from authoritative figures who model the desired behaviors. Moreover, this study shows the power of the sacred to inspire behavioral change, which, in the context of Buddhism, is cultivation of the bodhisattva ethic on the path to attaining enlightenment. The biggest difference between the two social contexts is that Taiwan’s Confucian cultural roots produced a relationship-based society, while American society is more institutional. This difference creates challenges for the groups in America; nevertheless, they have enjoyed some success among immigrants and people who resonate with them and appreciate their help. These Buddhists’ success in the U.S. and Taiwan shows that religion’s “power of the sacred” can have a positive effect in contemporary, post-modern society, when religious groups effectively reflect the immediate concerns of their local communities. Hence, the process by which these groups responded to the strain of environmental degradation by integrating pro-environmental teachings, practices, and behavioral norms into their spiritual cultivation and their deployment of local cultural symbols to facilitate adoption of those norms may serve as a pattern to other religious groups responding to environmental degradation in other communities.