Usual interstitial pneumonia (UIP) is the most common idiopathic interstitial pneumonia (IIP) and is associated with a poor prognosis and poor responsiveness to immunosuppressive therapy. We present a case of a woman with steroid-responsive biopsy-proven UIP with significant and sustained improvement in pulmonary function. A female in her 40s presented following a one-year history of progressive dyspnea, a 20 lb weight loss, and fatigue. Imaging of the chest with computed tomography (CT) showed bibasilar subpleural reticular opacities and minimal peripheral honeycombing. Comprehensive connective tissue disease (CTD) antibody testing was negative. Pulmonary function testing showed moderate impairment with reduction in forced vital capacity (FVC, 69% predicted), forced expiratory volume in one second (FEV1 73% predicted), and diffusing capacity for carbon monoxide (DLCO, 52% predicted). Surgical lung biopsy showed UIP with prominent inflammatory infiltrates. Following treatment with prednisone and azathioprine, the patient's symptoms resolved, while objective pulmonary function testing showed normalization of lung function, which is sustained at >4 years of follow-up. Improvement in lung function following immunosuppressive therapy is distinctly uncommon in either idiopathic or secondary UIP. This report suggests that occasionally, patients with secondary UIP occurring in the context of otherwise undefinable autoimmune clinical syndromes may be responsive to immunosuppressive therapy.