Although the structure of executive function (EF) during adulthood is characterized by both unity and diversity, recent evidence suggests that preschool EF may be best described by a single factor. The latent structure of EF was examined in 228 3-year-olds using confirmatory factor analysis. Children completed a battery of executive tasks that differed in format and response requirements and in putative working memory and inhibitory control demands. Tasks appeared to be age appropriate, with adequate sensitivity across the range of performance and without floor or ceiling effects. Tests of the relative fit of several alternative models supported a single latent EF construct. Measurement invariance testing revealed less proficient EF in children at higher sociodemographic risk relative to those at lower risk and no differences between boys and girls. At 3years of age, when EF skills are emerging, EF appears to be a unitary, more domain-general process.