Background Child-care centers are an integral part of life for many families with young children. American Indian children are at elevated health risk because of higher levels of obesity and associated health behaviors. Objective Our aim was to assess the child-care environment and children's physical activity (PA) and dietary intake in young children attending tribally affiliated child care. Design We conducted a cross-sectional study. Participants/setting Participants were from 11 tribally affiliated child-care centers across Oklahoma and included 82 children aged 3 to 5 years old. Main outcome measures Classroom observations were conducted using the Environmental and Policy Assessment Observation to measure PA and nutrition environments. Children wore an ActiGraph GT3X accelerometer and lunchtime plate waste was observed. Statistical analyses Descriptive statistics, including mean [plus or minus] standard deviation and frequencies, were calculated for the children's behaviors and environment. Results The total environment score was 23.9 [plus or minus] 5.2 (maximum=43). The nutrition score was 12.5 [plus or minus] 3.1 (maximum=21). The PA score was 11.7 [plus or minus] 2.2 (maximum=22). The participants were 3.8 [plus or minus] 0.1 years old, 55% were male, 67% were American Indian, and 38% were overweight or obese. Accelerometers were worn for 5.9 [plus or minus] 1.7 hours, excluding naptime. Children accumulated 4.3 [plus or minus] 2.2 min/h of moderate to vigorous PA, 4,294 [plus or minus] 1,883 steps/day, and 12.1 [plus or minus] 3.7 steps/min. At lunch, children were served 510 [plus or minus] 241 kcal, and consumed 387 [plus or minus] 239 kcal. Lunches consisted of 47% carbohydrate, 20% protein, and 33% fat. Total number of F/V served was 2.9 [plus or minus] 1.9 and consumed was 2.3 [plus or minus] 1.8, while whole grains served and consumed were 0.3 [plus or minus] 0.4 and 0.2 [plus or minus] 0.4, respectively, and lean proteins served and consumed were 0.3 [plus or minus] 0.4 and 0.2 [plus or minus] 0.4, respectively. Conclusions This study describes obesogenic aspects of the child-care environment and identifies areas for improvement. Children did not accumulate adequate PA or consume calories or fat excessively. Children consumed multiple F/V; however, more whole grains and lean proteins could be provided. Future research might investigate how the healthfulness of the child-care environment can be improved by counseling providers on nutrition and PA strategies to prevent obesity. (author abstract)