Following the sustainable consumption trend, sustainable tourism has emerged to support the environment by reallocating under-utilized resources and revitalizing the local community with the support of green P2P accommodation. This research aims to investigate what sustainability-related values (altruistic vs. egoistic) prompt consumers’ green P2P accommodation consumption and to pinpoint the psychological mechanism that drives such a green choice with the norm activation theory. A series of two studies were conducted to explore the answers to the research questions. The findings showed that consumers’ altruistic value resulted in significantly enhanced booking intention, whereas consumers’ egoistic value led to a much higher level of willingness-to-pay-more. Furthermore, the two PROCESS test results revealed the significant indirect effect of green advertisement (altruistic vs. egoistic) on both consumers’ booking intention and willingness-to-pay-more through the three serial mediating variables: awareness of consequence → ascription of responsibility → personal norm.