The concentrations of amoxicillin in pig plasma were determined by HPLC technique. Separation was achieved on a Lichrocart 250 x 4 mm Purospher column and detection was performed with a fluorescence detector. The mobile phase consisted of a mixture of acetonitrile with buffer solution (0.05 M KH₂PO₄, pH 5.6) delivered by a isocratic programme. For amoxicilin assay, the plasma samples were exposed to reaction with formaldehyde under acidic and heating conditions. The limit of detection and quantification, as well as the accuracy and precision of the method were evaluated from spiked plasma samples at concentration levels ranging from 10 to 500 ng‧mL⁻¹. Recovery of spiked amoxicillin was >91%, with coefficient of variation equals 0.12%. This method offers a rapid, repeatable, and accurate procedure and has been useful for determination of pharmacokinetic parameters of amoxicillin in pigs’ and poultry plasma.