This study was conducted to evaluate the depletion of residues of the antibiotics flumequine, oxytetracycline, sulfadiazine, trimethoprim, and oxolinic acid after in-feed administration to gilthead seabream. Fish were treated with the target antibiotics at doses of 30 mg/kg of body weight per day for 10 days at two seawater temperatures. Fish in each of five tanks were fed with a different medicated feed. After in-feed administration, five fish were randomly selected at different times, and antibiotic presence was analyzed in a mixture of muscle and skin. Antibiotic concentrations were determined through a validated analytical method based on liquid chromatography separation and mass spectrometry detection. Two trials were carried out with fish at different temperatures (14.0 and 19.5°C). Depletion of antibiotics occurred more rapidly at the higher temperature. Elimination rates for all antibiotics assayed were high, which indicates that the withdrawal period for these antibiotics could be reduced. The results suggest that in gilthead seabream maintained at these two temperatures no detectable concentrations of the antibiotics used in this study will remain in edible tissues 35 days after treatment. For flumequine and oxolinic acid, the elimination time is shorter (4 and 20 days, respectively).