Bronchorrhea is a watery sputum volume of at least 100 mL/day, which is commonly associated with lung malignancies. We report a 57-year-old woman was admitted to the hospital with a cough, profuse sputum. Chest CTs showed crazy paving pattern and lung nodules. Cell nests were visible on the Thinprep Cytologic Test. The case was considered an invasive mucinous adenocarcinoma of the lung combined with bronchorrhea. Significantly, the sputum volume declined rapidly and did not rise again when the patient was diagnosed with COVID-19 and treated with nirmatrelvir/ritonavir. This case is suggestive of studies related to regulatory mediators associated with bronchorrhea.