Pulmonary toxoplasmosis is a serious pulmonary condition caused by the protozoan Toxoplasma gondii It typically affects immunocompromised patients presenting acutely with cough, fever, myalgias, arthralgias and lymphadenopathy, and chronically with persistent cough and dyspnoea. Because of its protean features, it can mimic many more common lung conditions in the immunocompromised patient, including atypical pneumonia, Pneumocystis pneumonia and interstitial lung disease. In this article, we present the case of a 55-year-old woman who presented to our hospital with persistent dyspnoea and cough, initially suspected to have an arthritis-related interstitial lung disease. She received a final diagnosis of pulmonary toxoplasmosis after lung biopsy demonstrated Toxoplasma cysts, later confirmed by serology. Treatment with trimethoprim-sulfamethoxazole resulted in significant improvement of her respiratory symptoms after 3 months.