Oxytetracycline is an antibacterial agent used widely for therapy of systemic bacterial infections in farmed fish, Thailand. The pharmacokinetics of oxytetracycline after intrasinus and oral administration in giant tiger prawn was examined by using a rapid high-performance liquid chromatography (HPLC) method. The kinetics of oxytetracycline was described by a two-compartment model after intrasinus administration. The distribution half-life ( T 1/2 a = 0.089 h) of oxytetracycline was shorter than the elimination half-life ( T 1/2 b = 23.1 h). The kinetics of orally given oxytetracycline was fitted to a one-compartment model. The bioavailability was calculated to be 59.9%. The time required for drug absorption (TDA), defined as the time for absorption to reach 90% of the maximum level, was approximately 9 h. An apparent steady-state distribution (Vss: 0.41 L/kg) was found for oxytetracycline in the present study, which is smaller than in fish species.