Increasingly, HIV prevention efforts must focus on altering features of the social and physical environment to reduce risks associated with HIV acquisition and transmission. Community coalitions provide a vehicle for bringing about sustainable structural changes. This article shares lessons and key strategies regarding how three community coalitions located in Miami and Tampa, Florida, and San Juan, Puerto Rico engaged their respective communities in bringing about structural changes affecting policies, practices and programs related to HIV prevention for 12-24-year-olds. Outcomes of this work include increased access to HIV testing and counseling in the juvenile correctional system (Miami), increased monitoring of sexual abuse between young women and older men within public housing, and support services to deter age discordant relationships (Tampa) and increased access to community-based HIV testing (San Juan).