While anhidrosis in Horner’s Syndrome is a well-documented result of apical lung malignancies impinging on the sympathetic pathway traveling through the upper lobe of the lung, its opposite effect, hyperhidrosis, is a seldom reported consequence. Hyperhidrosis occurs as a result of irritation of the sympathetic nervous system near the superior cervical ganglion. In this report, we examine a patient with known Stage IIIB squamous cell carcinoma of the lung presenting with right hemifacial hyperhidrosis, dyspnea, and right upper extremity swelling. Computed tomography angiography (CTA) of the chest re-demonstrated the intrathoracic neoplasm encroaching on his mediastinum. During admission, the patient had his first cycle with carboplatin and paclitaxel. His hyperhidrosis, as well as dyspnea and swelling improved post-treatment, and the patient was stable for discharge to follow up outpatient with oncology and radiation oncology to continue further treatment. As hemifacial hyperhidrosis is rarely reported, it becomes important to recognize this as a likely indicator of mediastinal invasion from malignancy.