This article defines the concept of Infant and Early Childhood Mental Health (IECMH) and describes how it provides the foundation for lifelong health and well-being. The authors provide policy recommendations that include the need to: (a) establish cross-agency leadership for IECMH, (b) ensure Medicaid payment for IECMH services, (c) invest in prevention through mental health consultation, (d) train the workforce on IECMH, and (e) raise public awareness of IECMH.