Sudden unexpected infant death (SUID) is the leading cause of postneonatal infant mortality in the United States, with disproportionately high rates in Baltimore City and Baltimore County in Maryland. This Advocacy Case Study describes the collaboration between the City and County Child Fatality Review teams to decrease infant mortality. B’more for Healthy Babies, formed in 2009 by the Bureau of Maternal Child Health in Baltimore City with the goal of reducing infant mortality through policy change, service improvements, community mobilization, and behavior change has had a sustained effort to respond to SUID. Recognizing that infants born in Baltimore City often reside in Baltimore County (and vice versa), collaboration with Baltimore County has been essential to increasing B’more for Healthy Babies’ scope, reach, and effectiveness. Public health messaging campaigns, creation, and dissemination of a “SLEEP SAFE” testimonial video, and Safe Sleep Summits have involved caregivers, healthcare providers, and community partners. Outcomes of this ongoing collaboration demonstrate a decrease in sleep-related infant mortality rates. Our findings also highlight the need for continued, real time monitoring of sleep-related infant mortality trends with a coordinated, multidisciplinary, and crossjurisdictional response. This initiative can serve as a model of cross-sector communication that can be replicated in other similar geographic locations to further reduce SUID.