Furosemide is an off-label drug frequently used as a diuretic in neonates with oliguria and/or edema. Its clearance in preterm neonates is lower than in term neonates or children. We aimed herein to clarify furosemide clearance (CL) in very preterm (VP) neonates (< 28 weeks gestation) within the first two weeks of life and identify the factors predictive of the PK parameters, such as CL. Furosemide was administered at 0.5 or 1 mg/kg in a 0.5-h infusion via a syringe pump, and blood samples were drawn from an artery or vein after the intravenous injection. The serum furosemide concentration was measured using high-performance liquid chromatography. The PK parameters were then analyzed using Bayesian estimation. Thirteen blood samples were obtained from ten VP neonates after intravenous injection. The mean postconceptional age and mean postnatal days at exposure to furosemide was 26.9 weeks and 7.1 days, respectively. The estimated mean CL was 16.5 mL/kg/h. The mean distribution volume (Vd) and elimination half-life (t1/2) was 0.37 L/kg and 15.3 h, respectively. Furosemide CL was negatively associated with serum creatinine (SCr) [CL = 84.2 - 67.1 × SCr (mg/dL)]. VP neonates within the first two weeks of life had a higher CL than subjects in other preterm neonatal studies. The SCr level was the sole parameter influencing furosemide CL and might serve as a good index for furosemide dosing in VP neonates.