Concurrent chemotherapy and radiotherapy (CCRT) followed by durvalumab immune therapy in appropriate patients is considered to be the standard of care in most fit stage III non-small-cell lung cancer (NSCLC) patients. However, CCRT is a toxic treatment that affects all organ systems and may cause acute and permanent side effects, some of which may be lethal. Supportive care is therefore of utmost importance in this clinical setting. A group of experts from the European Society for Therapeutic Radiology and Oncology (ESTRO) and the European Society of Medical Oncology (ESMO) identified the following items of importance for further improvement of supportive care: smoking cessation; nutrition before and during CCRT (including treatment and prevention of anorexia); physical exercise before and during CCRT; prevention and treatment of acute esophagitis and dysphagia; treatment of cough and dyspnea; treatment of skin reactions; treatment of fatigue; prophylaxis of nausea and emesis; prevention, diagnosis, and treatment of cardiac disease and damage; and optimization of radiotherapy techniques and chemotherapy adjustments to reduce toxicity in the era of immune therapy. The resulting recommendations are summarized in this manuscript and knowledge gaps identified, in which future investments are needed to improve supportive care and hence quality of life and survival for our stage III NSCLC patients.