In The Netherlands, the 4-Skills Scan is an instrument for physical education teachers to assess gross motor skills of elementary school children. Little is known about its reliability. Therefore, in this study the test-retest and inter-rater reliability was determined. Respectively, 624 and 557 Dutch 6- to 12-year-old children were analyzed for test re-test and inter-rater reliability. All tests took place within the school setting. The outcome measure was age-expected motor performance (in years). Results showed a small practice effect of .24 years for re-test sessions and assessment of motor skills was possible with acceptable precision (standard error of measurement = 0.67 years). Overall, intraclass correlation coefficient (ICC) was .93 (95% confidence interval: 0.92-0.95) for test-retest reliability and 0.97 for inter-rater reliability. For the repeated measures, the smallest detectable change (SDC) was 1.84 and limits of agreement were -1.60 and 2.08 years. It can be concluded that the 4-Skills Scan is a reliable instrument to assess gross motor skills in elementary school children.