Purpose To describe adherence to sustainable healthy diets among a sample of 958 Chilean pre-schoolers (3-6 years) and explore associations between adherence and child and maternal sociodemographic and anthropometric characteristics.Methods Children's adherence to sustainable healthy diets was calculated from single multiple-pass 24-h dietary recalls using the Planetary Health Diet Index for children and adolescents (PHDI-C). Higher PHDI-C scores (max score = 150 points) represent greater adherence. Adjusted linear regression models were fitted to explore associations between PHDI-C scores and child and maternal characteristics.Results Children obtained low total PHDI-C scores (median 50.0 [IQR 39.5-59.8] points). This resulted from low consumption of nuts & peanuts, legumes, vegetables, whole cereals, and vegetable oils; a lack of balance between dark green and red & orange vegetables, inadequate consumption of tubers & potatoes and eggs & white meats, and excess consumption of dairy products, palm oil, red meats, and added sugars. Mean PHDI-C total score was significantly higher (50.6 [95%CI 49.6, 51.7] vs 47.3 [95%CI 45.0, 49.5]) among children whose mothers were >= 25 years compared to those with younger mothers. Positive associations were observed between scores for fruits and maternal education, vegetables and maternal age, added sugars and child weight status, while negative associations were observed between fruits and child age, and vegetable oils and maternal education. Scores for dairy products PHDI-C component were lower among girls.Conclusion Adherence to sustainable healthy diets was low among this sample of Chilean children and was significantly associated with maternal age, being lower among children whose mothers were younger.