Pursuing health equity necessitates recognizing health disparities that disproportionately impact disadvantaged groups and eliminating their barriers to essential health resources. Interactive digital technologies-specifically, popular social media platforms such as blogs and social networks-can be leveraged to engage underserved minority populations in collective social action aimed at addressing key determinants of health disparities and promoting equitable health outcomes. The present research focuses on the plight of African Americans-a minority group facing significant health disparities. Particularly in the domain of bone marrow donation, African Americans remain the group least likely to find a matching donor. Guided by the social comparison framing literature, we conducted an online experiment to investigate how group comparison information (GCI) emphasizing group-based disparities and supportive user comments on social media platforms influence African Americans' intentions to join a bone marrow registry. In doing so, we considered hope as a mediator and group identification as a moderator. Results based on a conditional process analysis showed that GCI led to greater bone marrow donor intentions in the presence of supportive comments through elicitation of hope, particularly among those low in group identification. The current findings demonstrate that it is important to consider the role of supportive message environments and group identification when addressing health disparities with GCI. Theoretical and practical implications are discussed.