During the infant and toddler years, there are many opportunities to promote emotional health, to prevent emotional disturbances from taking root, and to treat mental health problems before they can manifest into more severe problems later in life. Policymakers need to support a continuum of services delivered by trained professionals with a financing mechanism that covers the cost of services. Investing early in supporting the mental health of infants and young children will yield benefits later and will allow states to forgo much more costly interventions that all too often result when mental health challenges go unaddressed.