Early Childhood Mental Health Endorsement® (ECMH-E®) offers a credential for those whose work with or on behalf of children 3-6 years old and their families is informed by infant and early childhood mental health principles. Those who have earned ECMH-E demonstrate completion of specialized education, work, in-service training, and reflective supervision and consultation experiences that have led to competency in the promotion and practice of infant and early childhood mental health. In this article, we describe the development of the ECMH-E criteria as it grew from the Endorsement for Culturally Sensitive, Relationship-Focused Practice Promoting Infant Mental Health® created by the Michigan Association for Infant Mental Health.