There are 3.4 million children infected with HIV worldwide, with up to 2.6 million eligible for treatment under current guidelines. However, roughly 70% of infected children are not receiving live-saving HIV care and treatment. Strengthening case finding through improved diagnosis strategies, and actively linking identified HIV-infected children to care and treatment is essential to ensuring that these children benefit from the care and treatment available to them. Without attention or advocacy, the majority of these children will remain undiagnosed and die from complications of HIV. In this article, we summarize the challenges of identifying HIV-infected infants and children, review currently available evidence and guidance, describe promising new strategies for case finding, and make recommendations for future research and interventions to improve identification of HIV-infected infants and children.