Aims and objectives To investigate the developing course of postoperative pain in a Chinese sample of patients following thoracic surgery. Background Chronic postoperative pain following thoracic surgery including both thoracotomy and video‐assisted thoracic surgery is often reported. However, research on pain trends concerning this topic is scarce with a notable lack of culturally focused studies by nurses. Design A prospective observational study. Methods The sample included patients undergoing thoracotomy (n = 137) and video‐assisted thoracic surgery (n = 143). Pain intensity and interference of pain with function were assessed during hospitalisation (day 1 to day 7 postoperatively) and followed up by telephone at 2 weeks and then at 1, 2, 3 and 6 months after surgery. Results Moderate‐to‐severe pain when coughing and moving was reported in over 85% during hospitalisation, and a significant difference in pain was found between those undergoing a thoracotomy (61%) and those having video‐assisted surgery (34%). Many patients whose immediate postoperative pain was poorly managed tended to report high pain levels after discharge and continued to have clinically important chronic pain 6 months after surgery. The pain intensity mean score during movement in the first five postoperative days was an important predictor of clinically important chronic pain, and those experiencing severe acute pain during hospitalisation had a higher probability of developing chronic pain. Conclusions Postoperative pain after thoracic surgery warrants greater attention because those experiencing severe acute pain during hospitalisation have a higher probability of developing chronic pain. Aggressive pain management and multimodal analgesia are recommended to prevent long‐term suffering in patients. Relevance to clinical practice Chronic pain after thoracic surgery remains a challenge in clinical nursing. To improve pain management quality and to prevent the transition of acute postoperative pain to chronic pain, standardised practice protocols and comprehensive physician and nurse education are highly recommended.