For musculoskeletal complaints (MSCs) among adults, several risk factors are known, but the most important determinant is an earlier episode of MSCs. Research has shifted to younger ages, showing a high prevalence of MSCs among children and adolescents. Our purpose was to evaluate the prevalence of MSCs among those growing up from age 11 to 14 and to explore the role of several sociodemographic, growth and development, psychosocial, and lifestyle factors. Data collected at age 11 (n = 2651) and age 14 (n = 2522) in the ongoing Dutch Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study were used. Analyses included multiple logistic regression analyses using stepwise backward selection. The 1-year prevalence of any MSCs for at least 1 month increased from 15.8% at age 11 to 24.4% at age 14, and this was also found for upper extremity complaints (from 4.7% to 7.6%), back complaints (from 2.7% to 9.3%), and lower extremity complaints (from 11.9% to 14.7%). More MSCs were found among girls, those with sports injuries, those with sleeping problems, and those with daytime tiredness, although complaints at age 11 were by far the most important factor associated with MSCs at age 14 for all pain sites. This study showed that MSC is already common at an early age and that already at age 14 the factor with the strongest association is an earlier episode of MSCs. Sleeping problems and tiredness may also play a role in the early development of MSCs, either as determinant or as a consequence.