The objective of this study was the oral administration of trimetoprim sulfamethoxazole as a prophylactic therapy in Bennett’s Wallabies (Macropus Rufogriseus) through the use of operant conditioning. In the study participated 15 animals of different gender and age, all of them living at “La Aurora” National Zoo in Guatemala City, Guatemala. The investigation was divided in 2 stages, first the desensitization and conditioning of the animals and second the oral administration of the drug. Results indicated that 76% of the population had a positive response to the desensitization and conditioning, however only 20% consumed the 100% of the dose. In conclusion the operant conditioning is an excellent tool for desensitizing and creating a routine with zoo animals, but further investigation is required to determine the efficiency of the administration of an oral treatment on this species.