.Background and Objective: This study examined the role of preschool education in the development of psychomotor skills and social adaptation among primary school students in Tonekabon during the 2024-2025 academic year, emphasizing the preschool period's importance as a foundation for holistic child development.

Method: Employing a causal-comparative (ex post facto) design, the study sampled 361 students from a population of 6,000 (grades 1-3) via stratified random sampling. Instruments included the Preschool Education Questionnaire, the Lincoln-Oseretsky Psychomotor Scale, and the Pickel & Weissman Social Adaptation Questionnaire. After verifying normality via the Kolmogorov-Smirnov test, data were analyzed using MANOVA, Pearson correlation, and linear regression in SPSS.

Findings: MANOVA revealed a statistically significant positive relationship between preschool education and the combined dependent variables, with a substantial effect size ($\eta_p^2 = 0.445$ to $0.495$). Significant positive correlations were observed between preschool attendance and both psychomotor skills and social adaptation. Furthermore, regression analysis identified psychomotor skills as a significant positive predictor of social adaptation.

Conclusion: Completing preschool education is associated with enhanced neuromuscular coordination, self-confidence, and social acceptance, facilitating smoother school integration. Given the ex post facto design and lack of control for family socio-economic status, these associations should be interpreted as predictive rather than definitive causalities. To optimize student growth, qualitative improvements and the provision of motor and interactive facilities in preschool centers are strongly recommended.