Executive functions (EF) are key predictors of long-term success that develop rapidly in early childhood. However, EF's developmental trajectory from preschool to kindergarten is not fully understood due to conceptual ambiguity (e.g., whether it is a single construct or multiple related constructs) and methodological limitations (e.g., previous work has primarily examined linear growth). Whether and how this trajectory differs based on characteristics of children and their families also remains to be characterized. In a primarily low-income, racially and ethnically diverse, typically developing, urban sample, the present study employed confirmatory factor analyses to examine the construct of EF and latent growth curve modeling to examine nonlinear growth across five time points. Results indicated that the development of a single EF construct with partial measurement invariance across time points was best characterized as nonlinear, with disproportionately more growth during the preschool year. There was individual variability in EF trajectories, such that children with higher EF at preschool entry showed relatively steeper growth during preschool compared to low-EF peers. However, children with less EF growth in preschool had steeper growth in kindergarten, attenuating the gains of high-EF preschoolers and resulting in some convergence in EF by the end of kindergarten. Findings have implications for (1) examining EF development in early childhood with more specificity in future studies, (2) informing the timing of EF interventions in early childhood, and (3) identifying children for whom such interventions might be especially beneficial.