A 62-year-old man presented with dry cough one year after diagnosis of psoriasis vulgaris. Chest high-resolution computed tomography (HRCT) demonstrated ground-glass opacities in the lower lobes, which were consistent with nonspecific interstitial pneumonia (NSIP). Two years later, his respiratory and skin conditions were aggravated. The reticular shadows were worse on chest CT, and traction bronchiectasis and consolidation appeared. Retinoid treatment administered by a dermatologist was effective for the skin lesions; furthermore, the vital capacity increased and serum KL-6 level and alveolar arterial oxygen gradient decreased. Although a slight change on chest CT was seen during retinoid treatment, radiologic findings significantly improved after corticosteroid treatment. This case demonstrates that corticosteroid treatment may be an acceptable option for progressive interstitial pneumonia with psoriasis.