Antisynthetase syndrome (ASS) is a clinical subtype of idiopathic inflammatory myopathy, and interstitial lung disease is a common complication. The 44-year-old male patient had been treated for coronavirus disease 2019 (COVID-19) complicated by severe pneumonia 8 months earlier, and the pulmonary lesions worsened again after glucocorticoid tapering and discontinuation. Clinical manifestations included recurrent cough, sputum production, and shortness of breath, with diffuse ground-glass opacities in both lungs. After admission, a thorough medical history, comprehensive physical examination, and auxiliary tests including autoantibody profiles confirmed a diagnosis of ASS with positive anti-threonyl-tRNA synthetase (PL-7) antibodies, along with ASS-related nonspecific interstitial pneumonia. Community-acquired pneumonia patients with onset of interstitial lung disease should be clinically differentiated to rule out the possibility of connective tissue diseases. Respiratory viral infections may contribute to acute exacerbations of interstitial lung disease associated with connective tissue diseases, but their pathogenesis requires further exploration.