This is the case of a 67-year-old man who complained of chronic dry cough. A chest computed tomography (CT) scan revealed diffuse ground glass opacities (GGOs). Hypersensitivity pneumonia was suspected, and he was advised to avoid certain antigens. A month later, the diffuse GGOs had disappeared and the cough had improved. Three years later, however, he again exhibited GGOs on chest CT scan, and six months later, multiple nodules appeared in the lungs. Based on the pathological findings from the nodule obtained on surgical biopsy, the nodules were composed of CD20-positive large reactive lymphocytes. Therefore, he was diagnosed with diffuse large B cell lymphoma (DLBCL). CD20-positive lymphocytes were also present in the diffuse interalveolar septa. This invasion of malignant lymphoma to the interalveolar septa presented as GGOs on chest CT scan. We experienced a rare case wherein malignant lymphoma presented as diffuse GGOs and multiple pulmonary nodules.