Cerebrospinal fluid (CSF) rhinorrhea is a condition characterized by leakage of CSF from skull base through the nostril(s). It is commonly associated with trauma, surgery, infections of paranasal sinuses/skull base, and intracranial and skull base tumors. Among malignant causes, lung cancer is rarely associated with CSF rhinorrhea. Herein, we report the case of a 51-year-old lady who was initially diagnosed with metastatic lung adenocarcinoma (LUAC) with anaplastic lymphoma kinase (ALK) rearrangement and initiated on treatment with alectinib. She had good clinicoradiological response, but on follow-up developed CSF rhinorrhea that required surgical correction. We also discuss the proposed mechanisms associated with occurrence of CSF rhinorrhea in the setting of metastatic ALK-rearranged LUAC.