<p>Diabetic kidney disease (DKD) is a chronic microvascular complication of diabetes mellitus and a leading cause of chronic kidney disease worldwide. Microalbuminuria remains the current gold standard for the diagnosis and staging of DKD; however, it often reflects established renal injury rather than early pathological changes. Fatty acid–binding protein 1 (FABP1), a cytoplasmic protein abundantly expressed in the renal proximal tubules, is released into the urine in response to tubular damage. FABP1 plays an essential role in intracellular fatty acid transport and metabolism and may serve as a potential biomarker for tubular involvement in pediatric diabetic kidney disease. A case–control study was performed on 90 children (30 T1DM with DKD, 30 T1DM without DKD [non-DKD], and 30 controls). Albumin–creatinine ratio (ACR) and serum FABP1 were ELISA measured. FABP1 was significantly higher in the DKD group versus non-DKD (<i>p</i> = 0.026) and controls (<i>p</i> = 0.009). FABP1 positively correlated with ACR (<i>r</i> = 0.25, <i>p</i> = 0.018), total cholesterol (<i>r</i> = 0.25, <i>p</i> = 0.019), and LDL-C (<i>r</i> = 0.25, <i>p</i> = 0.017). A cutoff &gt; 189&#xa0;ng/L discriminated DKD from non-DKD (AUC = 0.67, sensitivity 63%, specificity 73%).</p><p><i>Conclusion</i>: Serum FABP1 may represent a complementary biomarker of tubular involvement in pediatric diabetic kidney disease.</p>