Global child health research plays a pivotal role in addressing inequities in children’s health and development worldwide. To achieve this goal, research must be based on sound scientific and ethical principles. This chapter focuses on ethics in child health research in low-, middle-, and high-income countries. It reflects on the key principles underlying ethical research in general and in global health research and child health research in particular. This is followed by a detailed discussion of 3 core principles underlying child health research: respect, benefit, and justice. Research with children poses important and universal ethical issues across world contexts, including establishing consent, protection from harm, privacy, and payment and gifts. Cultural, social, political, and economic factors that can interact to pose particular challenges with regard to these issues in different contexts, especially in low- and middle-income settings, are explored. As methodology and ethics are integrally linked, this chapter also examines the ways in which children have been included in health research studies: research on children, research with children, and research by children. This is followed by a brief discussion of ethical mechanisms that are in place to ensure that ethical standards are met and maintained in research on global child health. The chapter concludes with a discussion of the many positive changes in ethical research involving children in recent years. Emerging ethical challenges in the fields of genetics and genomics are highlighted.