This study examined longitudinal changes in motor competence and social behavior among elementary school students participating in a progressively structured traditional-games program based on Low Organized Games (LOG), Basic Lead-up Games (BLG), and Advanced Lead-up Games (ALG). A single-cohort longitudinal repeated-measures design was employed with 60 first-grade students aged 6–7 years (33 boys and 27 girls), all of whom completed seven measurement occasions (T0–T6), with no attrition in the analytical sample. Motor competence was assessed using the Test of Gross Motor Development–Third Edition (TGMD-3). In contrast, social behavior was assessed as a continuous, teacher-rated outcome using the School Social Behavior Scales (SSBS). Data were analyzed using descriptive statistics and repeated-measures ANOVA with Greenhouse–Geisser correction and Bonferroni-adjusted pairwise comparisons. Motor competence showed a consistent upward trajectory, with mean TGMD-3 total raw scores increasing from 42.73 at T0 to 91.18 at T6. The continuous social-behavior score also increased from 0.093 at T0 to 0.213 at T6. Significant changes over time were observed for motor competence, F(2.02, 119.11) = 53,371.75, p < .001, ηp² = .999, and social behaviour, F(2.51, 148.26) = 2,307.18, p < .001, ηp² = .975. All adjacent measurement comparisons were significant for both outcomes after Bonferroni adjustment. These findings show clear upward longitudinal trajectories in motor competence and social behavior during participation in the progressively structured traditional-games program.