Given the far-reaching effects of the COVID-19 pandemic, it is important to investigate how executive function (EF) assessments were impacted by changes in measurement protocols, context, and timing due to the pandemic. The present study used data from two projects. The first project occurred prior to the pandemic (N = 244, 44.67% female; Mage = 44.27 months) with teacher ratings and objective EF measures collected in the spring of preschool, fall of prekindergarten (pre-K), and spring of pre-K. The second study was comprised of two cohorts, a transition cohort (i.e., Fall 2019 to Fall/Winter 2020) and a post-COVID lockdown cohort (i.e., Fall 2020 to Fall/Winter 2021). For both cohorts, data were collected in the fall of pre-K, spring of pre-K, and fall/winter of kindergarten (N = 130, 46.2% female, Mage = 44.84 months). Aims included: (1) evaluating the measurement characteristics of a virtual assessment of EF, (2) examining cohort differences in teacher and objective EF measures, (3) testing longitudinal mean-level change in EF, and (4) evaluating associations between COVID impact and change in EF. Teachers reported a marginal decrease in EF for the transition cohort and no change in the post-COVID cohort, whereas objective measurements demonstrated the expected increase in EF. Child and family COVID-19 impact emerged as risk factors for reduced EF for the transition cohort but not the post-COVID cohort. Overall, this study provides novel evidence that the timing and type of EF assessment differentially impacted estimates of children's EF. (PsycInfo Database Record (c) 2023 APA, all rights reserved).