Renal dysfunction affects 5-18% of patients with sickle cell disease (SCD). To date, no studies have described urinary levels of transforming growth factor β-1 (TGF-β1), a marker of fibrosis, and neutrophil gelatinase-associated lipocalin (NGAL), a marker of acute/chronic kidney disease, as biomarkers in identifying patients at risk of developing renal disease in SCD. We hypothesized that SCD subjects will have increased urinary excretion of TGF-β1 and NGAL compared with healthy controls (CTR). We examined 51 SCD subjects: 42 HbSS, 8 HbSC, and 1 HbSD. Sixteen out of 42 patients with HbSS were on hydroxyurea (HU). Urinary excretion of TGF-β1 was 26.4 ± 1.5 pg/mgCr in SCD subjects vs 15.0 ± 2.4 pg/mgCr in CTR (p<0.00001). SCD patients with hemoglobin < 9 g/dl had higher urinary TGF-β1 than patients with milder anemia (p=0.002). Urinary TGF-β1 trended lower in HbSS patients treated with HU (23.61 ± 2.6 pg/mgCr), vs patients not on HU (27.69 ± 1.8 pg/mgCr; p=0.055). There was no correlation between urinary TGF-β1 and microalbuminuria or estimated glomerular function. There was no difference in urinary NGAL in SCD patients vs CTR. We suggest that urinary TGF-β1 may serve as a marker of early renal injury in SCD.