Treatment of a Leafy Sea Dragon, (Phycodurus eques), for mycobacteriosis was considered after the death of two tank-mates and when the remaining dragon displayed clinical signs of illness. Clinical signs observed included a decrease in active foraging for food, lethargy, dullness of body coloration, and abnormal resting posture. One of the two previous dragons was diagnosed with chronic mycobacteriosis both by bacterial culture and histopathology. Bacterial sensitivity of the isolated mycobacterium species revealed limited antibiotic sensitivity, specific to only ciprofloxacin and tetracycline. As ante mortem diagnosis of systemic diseases in Syngnathids is very difficult, a decision was made to begin antibiotic treatment in June 2004. Ciprofloxacin was selected as the antibiotic for weekly treatments. A dose of 100 mg/kg of body weight was administered orally by intubation with a bolus of frozen mysids. The dragon responded well to the weekly treatments after initial acclimatization to the procedure. During the course of the six month treatment, previously noted clinical signs resolved: coloration returned to normal, activity level and appetite dramatically increased, and resting posture returned to normal. In early December 2004, the health of the dragon precipitously declined and it died despite continued treatment. Necropsy and histopathology revealed disseminated granulomatous mycobacteriosis. Bacterial culture from lesions during necropsy revealed two atypical mycobacterium species, M. chelonae and M. fuerth.