We present a 35-year-old female patient who was started on rifampicin (900 mg orally once daily) and trimethoprim/sulfamethoxazole (TMP/SMX) (160/800 mg orally twice daily) after being diagnosed with brucellosis. Following defervescence and improvement in her general condition, fever recurred on the 12th day of treatment. A re-challenge drug test lead to causality assessment and treatment was switched to a combination of streptomycin (1 g intramuscularly) for 10 days and TMP/SMX (160/800 mg orally twice daily) for 4 weeks. Our patient is doing well after 12 months of follow-up.