Background: There is a lack of evidence regarding 24-hour movement behaviors of young children from low- and middle-income countries. This study examined Mongolian preschoolers’ adherence to the World Health Organization’s guidelines for physical activity, sedentary behavior, and sleep; their associations with health indicators, and the feasibility of the SUNRISE International study in Mongolia. Methods: Preschool-aged children were recruited from 5 kindergartens in urban and rural areas of Ulaanbaatar city and Tuv province in Mongolia. Physical activity and sedentary behavior were measured by an ActiGraph accelerometer worn for 5 consecutive days. Screen time and sleep were reported by parents. The National Institute of Health and Early Years Toolboxes were used to assess motor skills and executive function, respectively. Results: One hundred and one children participated in the study (mean age = 4.82 y, boys = 58), with 88% (n = 89) having complete data for analysis. The proportion of children who met the recommendations for physical activity, sedentary screen time, and sleep was 61%, 23%, and 82%, respectively. Only 7% met all recommendations. Meeting the sleep recommendation individually (P = .032) and in combination with the physical activity recommendation was associated with better gross (P = .019) and fine (P = .042) motor skills. Spending more time in physical activity was positively correlated with motor development. Results confirmed that the SUNRISE study protocol was feasible, age-appropriate, and enjoyable for children. Conclusions: The results of the SUNRISE pilot study will help inform the SUNRISE Mongolia main study and lay the groundwork for future research into children’s 24-hour movement behaviors in Mongolia.