Volunteer organizations face two challenges not found in non-volunteer organizations: recruiting and retaining volunteers. While social media use is increasing amongst individuals, its use and effectiveness for volunteer recruitment and retention by volunteer organizations is unknown. The dissertation reports the results of three studies to investigate this important question. Using a mixed-methods approach, it addressed the dual nature of social media and its effectiveness by including volunteer organizations and social media users. This dissertation found that although volunteer organizations are not using social media effectively, they could virtualize requirements of the recruitment process by focusing on relatable events instead of sterile marketing. This dissertation contributes to information systems literature by extending the post-acceptance model of IS continuance to show that social media mediates volunteer continuance. It further contributes by revealing a potential new area of research, i.e., the use and effectiveness of online social media for volunteer organizations.