One of the factors associated with high-quality early care and education is the qualifications of teachers and caregivers working with young children. However, due in part to the large variation in teacher and caregiver preparation pathways and requirements across states and settings, it can be difficult to determine the specific effects of teacher education and credentials on practice or child outcomes. This brief summarizes the findings from an evidence review conducted to address the research question: What evidence do we have from the research literature about associations between infant/toddler teacher and caregiver preparation (e.g., education, credentials, etc.) and improvements in quality and child outcomes? A review of the recent literature (most published between 2005 and 2015) identified 31 studies that had relevant information to address the research question. The scant evidence that is available regarding associations between infant/toddler teacher and caregiver preparation and outcomes is generally positive, but still somewhat mixed. This is true regardless of whether the preparation is indicated by educational attainment, degree type (e.g., concentration or major in early childhood or a related field), or training. There is insufficient evidence to support conclusions on the associations between state infant/toddler credentials and observed quality or child outcomes in the studies reviewed. The broader literature focused on teachers and caregivers of children ages zero to 5 also reveals mixed findings. Much of the literature focuses on educational degrees without more refined assessment of individual competencies or the content of coursework or training. Also, current data sources do not make it easy to look for minimum or baseline levels of preparation associated with quality care and child outcomes. More research is needed examining the associations between state credentials and required core competencies within the credentials and observed quality and outcomes. Such research would help to inform policy priorities and practice, with the goal of improving outcomes for our very youngest children and their families. (author abstract)