Background and Objective. Research has shown that children’s motor performance (MP) and body composition (BC) are positively related to health and influence physical activity across the lifespan. As an intervention for improving MP and BC in childhood, engagement in a sports club (SC) is an important key strategy. Therefore, the aim of the study is to examine the stability of MP and BC and their associations with SC participation. Methods. MP and BC of 295 children (161 girls) with a mean age of 8.42 ± 0.36 years were measured annually with the German Motor Test 6‐18. Based on self‐reports, children were divided into three groups according to consistent (CON), partial (PAR), and nonparticipation (NO) in SC. NO and PAR were then combined into NO‐PAR. The stability of MP and BC was determined using Pearson’s correlation coefficient (r). Associations of SC participation, MP, and BC were examined using robust mixed‐model ANOVA (mmANOVA) additionally with first grade as covariate (ANCOVA). Results. More girls (39%) than boys (25%) were classified in PAR. The stability of MP (r = .755) and BMI (r = .889) was moderately high. Children in CON (r = .847) showed lower stability in BMI than NO‐PAR (r = .923). mmANOVA revealed better overall MP for both sexes in CON except for balance and BMI. Boys in CON showed better performance in flexibility, endurance, and speed than NO‐PAR. ANCOVA confirmed unadjusted results for boys. Conclusion. Lower stability of BMI due to CON indicates a greater variance in ranking and thus the chance to adjust weight management in childhood. Girls’ MP benefited less from SC participation, which may be due to their more frequent rates in PAR. Therefore, interventions to increase engagement in SC should focus on a stepwise approach from none to partial and finally to long‐term participation.