The use of social media in nonprofit professional membership organizations affects how leaders communicate with members, consumers, the community, and other stakeholders. The purpose of this qualitative multiple case study was to explore the social media marketing strategies that leaders in nonprofit professional membership organizations use to keep their organizations sustainable. Data were collected from 5 social media marketing leaders representing 5 nonprofit professional membership organizations in the Chicago region. Data collection occurred through semistructured interviews, review of organizational documents pertaining to social media marketing strategies, and review of the social media sites and websites of the participants' organizations. Rogers's diffusion of innovation theory served as the conceptual framework for this study. A thematic analysis of the data yielded 4 themes: social media platforms and engagement strategies, social media content, social media challenges, and brand awareness. Leaders of nonprofit professional membership organizations who want to gain a competitive edge by using the appropriate social media platforms, creating quality content, overcoming challenges, and increasing brand awareness might choose to align with the strategies identified in this study. The findings of this study could help organizational leaders use social media marketing strategies effectively for engagement and organizational sustainability. The implications for positive social change arising from the use of social media by leaders in nonprofit professional membership organizations include opportunities to connect with and engage the public to build stronger communities through collaboration.