A pharmacokinetic study of oxytetracycline (OTC) following a single (100 mg kg−1) or a multi-dose (100 mg kg−1 for 5 days) oral administration was carried out in yellow catfish, Pelteobagrus fulvidraco. After oral administration at 25°C, a one-compartment model was developed. The absorption half-life (t1/2(ka)) was 3.92, 1.44, 2.75, and 3.34 h in plasma, muscle, liver, and kidney after the single dose, and 0.35, 0.22, 0.42, 0.32 h after the multi-dose, respectively. The order of peak concentration (Cmax) was liver > kidney > plasma > muscle, at 3.48 μg g−1, 2.90 μg g−1, 1.46 μg ml−1, and 1.39 μg g−1 after the single dose, and 14.02 μg g−1, 8.51 μg g−1, 4.17 μg ml−1, and 3.84 μg g−1 after the multi-dose, respectively. The elimination half-lives (t1/2(ke)) of OTC in plasma, muscle, liver, and kidney were calculated to be 7.64, 26.29, 19.08, and 10.61 h after the single dose, and 47.54, 70.99, 49.87, and 47.73 h after the multi-dose, respectively. The results suggest that OTC was absorbed faster after the multi-dose than after the single dose, suggesting that OTC could be more efficacious after the multi-dose and more effective in the control bacterial diseases in aquaculture, with the side effects of longer withdrawal periods.