As community-level interventions become more common in HIV prevention, processes such as community mobilization (CM) are increasingly utilized in public health programs and research. Project Accept, a multi-site community randomized controlled trial, is testing the hypothesis that CM coupled with community-based mobile voluntary counseling and testing and post-test support services will alter community norms and reduce the incidence of HIV. By using a multiple-case study approach, this qualitative study identifies seven major community mobilization strategies used in Project Accept, including stakeholder buy-in, formation of community coalitions, community engagement, community participation, raising community awareness, involvement of leaders, and partnership building, and describes three key elements of mobilization success.