A 4-month-old, intact male Boxer puppy was presented to the Animal Emergency and Critical Care Services of South Florida because of nasal discharge, dehydration, dyspnea, and coughing. The dog had been diagnosed with intestinal parasites and kennel cough approximately 10 days before presentation. Lateral and ventrodorsal radiographs of the thorax revealed an increased bronchointerstitial pattern throughout the lungs. A transtracheal wash was performed. On cytologic examination of direct, Wright-Giemsa-stained smears, small basophilic coccoid structures (0.3-0.9 microm in diameter) were observed in low to moderate numbers within neutrophils and adherent to epithelial cells. The small size of the organisms raised suspicion for Mycoplasma. Culture of the transtracheal wash fluid resulted in growth of a Mycoplasma sp. The patient was treated with enrofloxacin and amoxicillin/clavulanate and made a full recovery. Recognizing Mycoplasma in transtracheal washes could aid in recommending the appropriate culture media or immunologic techniques, which could result in an accurate diagnosis of mycoplasmosis.