Objective Knowledge about childhood functional somatic symptoms (FSS) and healthcare costs is scarce. This study aims to assess whether FSS in children aged 5-7 years are associated with increased future primary healthcare. Design At baseline of the observational cohort study, between years 2005 and 2007, 1327 children from the Copenhagen Child Cohort were assessed at ages 5-7 years for FSS and chronic physical diseases using the Soma Assessment Interview. Information on primary healthcare use was obtained from the National Health Insurance Service Register, and measured as the price of all medical services outside the hospital during a 4.5-year follow-up period from the day of assessment. Regression with bootstrap bias-corrected and accelerated CIs were performed. Results 1018 (76.8%) children had no FSS with primary healthcare use adjusted for other child health problems, maternal education and family changes of 448.2, 388.2-523.8 and number of face-to-face contacts: 11.90, 10.71-13.25; 250 (18.9%) had FSS with healthcare use 441.0, 355.0-550.3 and face-to-face contacts: 11.22, 9.60-12.91, and 58 (4.4%) had impairing FSS with healthcare use: 625.9, 447.9-867.8 and face-to-face contacts: 14.65, 11.20-19.00. In unadjusted regression analysis, impairing FSS were associated with increased healthcare use (increased costs: 246.0, 67.6-494.3). The adjusted association was slightly attenuated (increased costs: 177.8, 1.3-417.0). Conclusions Impairing FSS in children aged 5-7 years is a predictor for the child's future primary healthcare use. More research on complex predictive models is needed to further explore the clinical significance of these results, and to contribute to the underpinning of early interventions towards impairing FSS in children.