Tyrosine kinase inhibitors (TKIs) of epidermal growth factor receptor (EGFR) were previously the standard first-line treatments for lung cancers with activating EGFR mutations. The first-generation reversible EGFR TKIs, gefitinib and erlotinib, demonstrated substantial efficacy in the treatment of brain metastases from EGFR-mutated lung adenocarcinoma. However, the efficacy of afatinib, the second-generation irreversible EGFR TKI, as the first-line treatment in lung adenocarcinoma patients with brain metastasis has yet to be evaluated.Here, we report cases of 3 patients who received afatinib alone as the first-line treatment in combination with whole-brain radiotherapy or following surgical resection of brain metastases. All 3 patients had EGFR L858R mutation. The first patient had lung adenocarcinoma with brain metastasis and no neurologic symptoms. After consultation, she received afatinib as a first-line treatment. Chest computed tomography and brain magnetic resonance imaging (MRI) showed partial response. The second patient had lung adenocarcinoma accompanied with a metastatic brain lesion associated with seizures. This patient received whole-brain radiotherapy and afatinib treatment following brain MRI and subsequently showed significant regression of the brain metastasis. The third patient had strabismus of the right eye, and brain MRI showed a single tumor at the cerebellar pontine angle. This patient underwent surgical resection of the tumor followed by afatinib treatment. He refused adjuvant radiotherapy after surgery for brain metastasis. The brain MRI showed no recurrent brain metastasis, and the patient had relatively less neurologic deficiency.This series of 3 cases indicate that afatinib may be an appropriate first-line treatment alternative in patients having lung adenocarcinoma with EGFR mutations. Further retrospective analyses and prospective clinical trials are required to substantiate the efficacy of afatinib in the treatment of brain metastases of lung adenocarcinoma.