Green sea turtles are widely distributed in tropical and subtropical water. Adult green sea turtles face many threats, primarily from humans, including injuries from boat propellers, being caught in fishing nets, pollution, poaching, and infectious diseases. To date, limited pharmacokinetic information is available in green sea turtles. Therefore, this study was conducted to evaluate the pharmacokinetic characteristic of marbofloxacin in the green sea turtle, Chelonia mydas, following single intravenous (IV) or intramuscular (IM) administration with marbofloxacin at dosages of 2 and 4 mg/kg body weight (BW). Blood samples were collected at pre-assigned times. Marbofloxacin concentration in plasma was extracted using liquid-liquid extraction, and analyzed by a validated high performance liquid chromatography (HPLC). Marbofloxacin was measurable from 15 minutes (min) to 168 hours (h) after IV and IM administrations at two dose rates. A non-compartmental model was used to fit the plasma concentration of marbofloxacin versus time curve for each green sea turtle The t 1/2 value of 49–52 h indicated that the overall rate of elimination of marbofloxacin in green sea turtles is quite long. The average IM bioavailability (F%) was more than 80%. Marbofloxacin is concentration-dependent drug, and area under the curve (AUC)/minimum inhibitory concentration (MIC) or the maximum plasma concentration (Cmax)/MIC is the best pharmacokinetic/pharmacodynamic (PK/PD) predictor for its efficacy. The dosage of marbofloxacin administered in this study seems to produce appropriate PK-PD parameters that predict antibacterial success for disease caused by susceptible bacteria. PK‐PD index, IM administration of marbofloxacin at a dosage of 2 mg/kg BW might be appropriate for initiating treatment of susceptible bacterial infections in green sea turtles, however further study of multiple doses and plasma binding protein are warranted to confirm an appropriate dosage regimen.