To address gaps in the availability of validated measures that assess early childhood teachers' workplace experiences, the current study examined the validity of the Early Childhood Teacher Experiences Scale (ECTES) for use in a diverse Head Start program. Mean differences in the ECTES dimensions of self-efficacy, job stress, and school support were examined across teachers' demographic characteristics and observed teacher-child interaction quality. Multilevel models examined associations between ECTES dimension scores and children's social-emotional and academic skills (N = 161 preschool teachers and N = 3,152 children). Findings support the reliability and validity of the three-factor structure of the ECTES in the diverse Head Start teacher sample. Higher teacher-reported self-efficacy and school support were associated with higher observed classroom emotional support, instructional support, and classroom organization. Higher teacher-reported self-efficacy was associated with fewer years of teaching experience. With respect to child outcomes, higher teacher self-efficacy and school support were associated with lower behavior problems and higher social-emotional skills but were not associated with academic skills. Implications of the findings, limitations, and future directions are discussed.