Background <p>Serum and urinary uromodulin are emerging as potential cardiovascular risk factors. The aim of our study was to determine uromodulin in both serum and urine to evaluate their potential as early cardiovascular risk markers and markers of kidney function in children and young adults.</p> Methods <p>This case–control study included 72 participants — 42 children and young adults with chronic kidney disease stages 1–2 and 30 healthy controls. Serum and urinary uromodulin concentrations were determined along with anthropometric measurements, body composition, and standard laboratory measurements in cardiovascular and kidney health assessment.</p> Results <p>Urinary uromodulin-to-creatinine was significantly decreased in the group with chronic kidney disease (<i>p</i> &lt; 0.001). It also correlated significantly with anthropometric measurements, systolic pressure, creatinine (but not with glomerular filtration rate), urate, and homocysteine. Serum uromodulin did not differ from healthy control subjects. Serum uromodulin correlated significantly with albuminuria, showing its minor potential in kidney health assessment in the young.</p> Conclusions <p>Urinary uromodulin is a better predictor of kidney and cardiovascular early damage than serum uromodulin in children and young adults with only mild chronic kidney disease. In at-risk individuals, lower urinary uromodulin levels might reflect a reduced functional kidney and cardiovascular reserve. Further research in the pediatric population is warranted.</p> Graphical Abstract <p></p>