The pharmacokinetic of norfloxacin (10 mg kg-1) following single intravenous (IV) and oral administration (PO) in healthy goldfish were investigated. Also, repeated (PO) administration of norfloxacin in healthy and experimentally Aeromonas hydrophilia infected goldfish was studied. Following IV administration, norfloxacin obeyed a two compartments open model, distribution half-life (t1/2(α)) equal to 0.12 h, volume of distribution (Vdss) was 1.01 L kg-1, elimination halflife (t1/2(β)) was 4.30 h and total body clearance (CLtot) was 0.17 L kg-1h-1. Following PO administration, norfloxacin was rapidly and efficiently absorbed through gastrointestinal tract as the absorption half-life (t1/2(ab)) was 0.84 h. Maximum serum concentration (Cmax) 4.10 μg ml-1, was achieved its maximum time (tmax) at about 2 h post administration and the elimination half-life (t1/2(el)) was 3.91 h. Oral bioavailability was 57.63% indicating moderate absorption of norfloxacin from oral site. Serum concentrations of norfloxacin following repeated PO administration of 10 mg kg-1 BW once daily for 5 consecutive days, were significantly lower in experimentally Aeromonas hydrophilia infected goldfish than in healthy ones. Based on these pharmacokinetics parameters determined, a dosage of 10 mg kg-1 BW given orally every 24 h in goldfish can maintain effective plasma concentrations with Aeromonas hydrophilia infection with (minimum inhibitory concentration) MIC90 ≤ 0.25 μg ml-1. Therefore, norfloxacin may be an effective therapy for goldfish diseases.