Background Resistin is a hormone, mainly produced in macrophages and monocytes, believed to play an important role in the inflammatory response. It has been linked to several chronic diseases such as heart failure, inflammatory bowel disease, and insulin resistance. Pediatric reference levels are needed for the risk stratification and interpretation of individual serum resistin concentrations. Methods A total of 1191 healthy, non-obese Danish schoolchildren (727 girls) aged 6–18 years (median 11.9) were included. Fasting serum resistin concentrations were quantitated by Human Resistin ELISA Development kit, Duo Set (R&D Systems) following optimization. Results The overall median resistin concentration was 8.93 ng/mL (interquartile range (IQR): 6.19–13.33, range 1.57–35.84) in boys and 10.42 ng/mL (IQR: 7.25–15.68, range 1.60–44.00) in girls. The resistin concentration correlated to relative BMI in both boys (p = 0.02) and girls (p < 0.0001). Percentiles for each age group were calculated alongside smoothed percentile curves and an age correlated increase was demonstrated, albeit only in girls (p = 0.02) and not in boys (p = 0.35). Conclusion Fasting serum resistin concentrations differ between sexes in healthy children and adolescents and are correlated both with the sex- and age adjusted BMI, and in girls to age.