Despite significant advances in pediatric HIV treatment, too many children remain undiagnosed and thus without access to lifesaving antiretroviral therapy. It is critical to identify these children and initiate antiretroviral therapy as early as possible. Although the children of HIV-infected adults are at higher risk of infection, few access HIV testing services because of missed opportunities in existing case finding programs. Family testing is an index case finding strategy through which HIV-infected patients are systematically screened to identify family members with unknown HIV status. By specifically targeting a high-risk population, family testing is a pragmatic, high-yield, and efficient approach to identify previously undiagnosed HIV-infected children and link them to care before they become symptomatic. Despite this, incorporation of family testing into national guidelines and implementation of this case finding approach is variable. In this article, we review the evidence base for family testing, describe its challenges, and provide guidance and sample tools for program managers aiming to integrate family testing into existing health systems.