The incidence of tumors during pregnancy comprises 0.1% of all malignant tumors. Breast cancer, cervical cancer, melanoma, ovarian cancer, leukemia, and lymphoma are the most common malignant tumors that occur during pregnancy. The less common cancers include gastrointestinal, urological, and lung cancers. The patient was 34 years old, 30 weeks of gestation, and a nonactive cigarette smoker, but exposed to passive cigarette and biomass smoke. She was diagnosed with hemoptysis two days ago. On physical examination, respiratory sounds decreased at the left baseline. Computerized tomography (CT) of the chest revealed a 32 × 79 mm mass lesion with irregular borders in the basal anterior of the left lung. A fiberoptic bronchoscopic examination was performed, and biopsies that were taken from the patient's airways with mucosal irregularity in the basal posterior of the left lung were consistent with adenocarcinoma. Estimated glomerular filtration rate (EGFR), anaplastic lymphoma kinase (ALK), and proto-oncogene tyrosine-protein kinase-1 (ROS-1) mutations were not detected. No brain metastases were detected. After delivery, two cycles of cisplatin–gemcitabine chemotherapy were administered. Multiple metastases were detected in the scalp, cervical, and thoracic regions. Due to neck pain caused by cervical metastasis, palliative radiotherapy was applied. During chemotherapy, the patient started to have severe headaches, and brain magnetic resonance imaging (MRI) was repeated for this reason. Multiple metastatic lesions were found in the brain MRI, and palliative cranial radiotherapy was started. The patient, whose chemotherapy was completed for six cycles, died 8 months after the diagnosis. Lung cancer can be diagnosed during pregnancy, and its prognosis is poor. This should be kept in mind by clinicians.