Background: In Western countries, about a quarter of children are affected by parental separation and a number of authors have previously investigated how familial structure impacts children's health. The purpose of the work: to analyze the psychomotor development of children aged 28 to 32 months based on family structure (parents together or separated), independently of the influence of socio-economic environment that is well documented. To analyse the psychomotor development of children younger than 3 years based on family structure (parents together or separated) independently of the influence of socio-economic environment that is well documented. Methods: Cross-sectional study by examination of 28 871 children as part of a free preventive medicine consultation. The data came from an assessment conducted 28 to 32 months after birth during which information was collected about the psychomotor development: to perform a standing jump, dress themselves, draw a vertical line and circle, use the "I" pronoun, build a three-word sentence, and say their first name Results: Ten percent of the children had separated parents. Compared to parents who were together, when adjusting for the socioeconomic environment, as well as all potential confounders, the adjusted odds ratios (ORs) (95 % confidence interval [CI]) for children with separated parents, in terms of their ability to perform a standing jump, dress themselves, and draw a vertical line and circle were respectively 0.9 (0.7-1.1), 1.1 (0.9-1.2), 1.3 (1.1-1.4) and 1.2 (1.1-1.4). The adjusted ORs (95 % CI) for children's inability to say the "I" pronoun, build a three-word sentence, and say their first name were respectively 1.2 (1.1-1.3), 1.3 (1.2-1.5), and 1.2 (0.9-1.5). Conclusions: After adjusting for sociocultural factors and other potential confounders, we observed that the children exhibited slower progression in psychomotor development, especially in language and graphic abilities when their parents were separated. While the implications of our study are somewhat limited, they do provide us with the necessary arguments enabling us to set up a prospective cohort study. Such a study should be able to better assess the impact of parental separation on the child's development, confirming our preliminary results.