Radical surgery with systematic upper mediastinal node dissection for primary lung cancer can cause recurrent laryngeal nerve (RLN) paralysis, but this is poorly reported. We retrospectively reviewed the clinical data for consecutive patients who underwent radical surgery for primary lung cancer with an observation period of at least 12 months. During follow-up, hoarseness and vocal fold movement were assessed clinically and laryngoscopically, respectively. Of the 365 patients included in this study, 22 (6.0%) experienced hoarseness as a complication. All 22 patients who experienced hoarseness had undergone upper mediastinal node dissection. Although 1 of the 22 patients refused to undergo laryngoscopy, we assessed the vocal fold movement in the remaining patients (95.5%). Among these, 5 patients (23.8%) had right RLN paralysis, and 15 (71.4%) had left RLN paralysis and showed no sign of RLN paralysis. Over 1-24 months, vocal cord movement improved in 61.1% (11/18); and over 1-28 months, hoarseness improved in 72.7% (16/22). All patients with right RLN paralysis improved without further treatment. We conclude that extensive follow-up is necessary to discern whether hoarseness is a temporary or permanent complication of radical surgery in patients with primary lung cancer who have undergone systematic lymph node dissection.