An ultra-high-performance liquid chromatograph-tandem mass spectrometry (UPLC/MS/MS) method was developed for the determination of amoxicillin sodium and tylosin tartrate in swine plasma. Amoxicillin sodium and tylosin tartrate were orally administrated to swine, and the pharmacokinetics were evaluated in plasma samples by UPLC/MS/MS after solid phase extraction. The linear range for amoxicillin sodium was 0.06–1 ¼Àg/mL (r² = 0.9975) and that for tylosin tartrate was 0.5–50 ng/mL (r² = 0.9994). The limit of quantitation and limit of detection for amoxicillin sodium were 0.2 ¼Àg/mL and 0.06 ng/mL, respectively, and the corresponding values for tylosin tartrate were 1.7 ng/mL and 0.5 ng/mL. The intra- and inter-day coefficients of variation were <9.8 % for amoxicillin sodium and <13.5 % for tylosin tartrate. The absolute recoveries of amoxicillin sodium and tylosin tartrate from swine plasma were 67 % and 72 %, respectively. The method showed excellent specificity, accuracy, precision, recovery, and stability. The pharmacokinetics of amoxicillin sodium (15 mg/kg) and tylosin tartrate (10 mg/kg) in healthy swine after administration of a single or compound dose were evaluated. Tylosin influenced the pharmacokinetics of amoxicillin, but amoxicillin did not affect tylosin.