Amoxicillin (AMX) has been commonly used to treat bacterial disease in striped catfish (Pangasianodon hypophthalmus) aquaculture in Vietnam. The aims of this study were to determine the pharmacokinetics parameters of AMX in striped catfish plasma, kidney and liver, as well as its withdrawal time in striped catfish muscle. AMX levels were determined using high-performance liquid chromatography mass spectrometry. Pharmacokinetics parameters were investigated through oral administration by the gavage method at a single dose of 50 mg AMX kg-1 body weight, blood and tissue sampling were done at 0.5, 1, 2, 4, 6, 12, 24, 72 and 96 hours post-administration of AMX. The absorption of AMX followed oral administration was fast, the time to get maximum concentration in plasma (Cmax = 127.5 ng mL-1) was 1 hour. The maximum concentration of AMX in kidneys was 3 times as high as that in plasma and Tmax in this organ was the longest at 8 hours compared with 1 hour in plasma and liver. The Cmax of the investigated organs were in the order of kidney > liver > plasma. The relationship of pharmacokinetics/pharmacodynamics (PK/PD) was estimated based on the curves of AMX concentration of plasma, liver and kidney over the minimum inhibitory concentration (MIC) of AMX, i.e., 135 ng mL-1 against Edwardsiella ictaluri, it was indicated that the time during which the kidney AMX concentration was above the MIC (T>MIC) was about 10 hours, but it was low in liver at about 1 hour. The withdrawal time of AMX was determined after feeding medicated feed once a day for five consecutive days at the dose of 50 mg AMX kg-1 body weight. Fish muscle was collected on day 1 and day 5 during medication and 6, 12, 24 and 72 hours after administration. Based on the maximum residue limit (MRL) of 50 µg kg-1 set by the Commission of the European Communities (EU), the withdrawal time of AMX in composite muscle and skin samples of striped catfish was 11 hours (at 30°C) after the last day of medication.