Purpose: To examine the associations among preschoolers fundamental motor skills, screen-time, physical activity (PA), and sedentary behavior (SB). Methods: Children ages 3-4 years were enrolled in a prospective observational trial of PA. Trained assessors conducted the Test of Gross Motor Development-3rd edition (TGMD-3), and the Movement Assessment Battery for Children-2nd edition, and parent-reported child screen-time and sociodemographic information. Children wore an accelerometer for 7 days to examine SB and total PA (TPA). TPA was further characterized as moderateto-vigorous PA (MVPA) or vigorous PA (VPA). Mixed linear models were calculated, controlling for age (for TGMD-3), sex, household income, and accelerometer wear time (for accelerometry models), with childcare center as a random effect. The primary analysis reported on the cross-sectional baseline data of 126 children with complete fundamental motor skill and screen-time data; a subanalysis included 88 children with complete accelerometry data. Results: Children were 3.4 +/- 0.5 years of age (54% girls; 46% white, 42% African American, 12% other). A total of 48% lived in households at or below the federal poverty level. Children engaged in 5.1 +/- 3.6 h/day of screen-time. Children's screen-time was inversely related to the Movement Assessment Battery for Children-2nd edition, manual dexterity skills percentile (beta (SE) = -1.7 (0.8), p = 0.049). In the accelerometry subsample, children engaged in 5.9 +/- 0.9 h/day of TPA of which 1.7 +/- 0.6 h/day was MVPA. Boys engaged in more MVPA and VPA and less SB compared with girls (all p < 0.05). A higher TGMD-3, total score (beta (SE) = 0.4 (0.2), p = 0.017) and locomotor score (beta (SE) = 0.7 (0.3),p = 0.018) were associated with more VPA but not with TPA or MVPA. Screen-time and television in the bedroom were not related to SB, TPA, MVPA, or VPA. Conclusion: Children's motor skills were positively related to VPA but inversely related to screen-time. Further inquiry into the implications of high exposure to screen-time in young children is needed. (C) 2019 Published by Elsevier B.V. on behalf of Shanghai University of Sport.