Abstract: As social media use on mobile devices has been integrated in people’s daily lives, corporations began to target the publics on corporate social responsibility (CSR) activities on mobile devices. In the context of a natural disaster, this study examines how publics respond to CSR-based initiatives by way of mobile corporate social responsibility (mCSR), including gratifications, social media engagement, perceived CSR motives, and the relationship outcomes as associated with mCSR practice. An online survey was conducted by sampling with 1,433 nationally representative adults in the United States. Findings indicated that four broad types of gratifications, such as technological convenience, social interaction, recreation, and information exchange, significantly influenced relationship outcomes such as satisfaction, commitment, distrust, trust, and control mutuality. Results also demonstrated that perceived CSR motives and social media engagement on mobile devices were significantly related to relationship outcomes, providing empirical evidence for the important role and potential mCSR communications can play in engaging publics and cultivating relationships during natural disasters.