Background: To examine long-term-survival of cT4 cN0/1 cM0 non-small-cell lung carcinoma (NSCLC) patients undergoing definitive radiochemotherapy (_ccRTx/CTx) in comparison to the trimodality treatment, neoadjuvant radiochemotherapy followed by surgery, at a high volume lung cancer center. Methods: All consecutive patients with histopathologically confirmed NSCLC (cT4 cN0/1 cM0) with a curative-intent-to-treat _ccRTx/CTx were included between 01.01.2001 and 01.07.2019. Mediastinal involvement was excluded by systematic EBUS-TBNA or mediastinoscopy. Following updated T4-stage-defining-criteria initial staging was reassessed by an expert-radiologist according to UICC-guidelines [8th edition]. Outcomes were compared with previously reported results from patients of the same institution with identical inclusion criteria, who had been treated with neoadjuvant radiochemotherapy and resection. Factors for treatment selection were documented. Endpoints were overall-survival (OS), progression-free-survival (PFS), and cumulative incidences of isolated loco-regional failures, distant metastases, secondary tumors as well as non-cancer deaths within the first year. Results: Altogether 46 consecutive patients with histopathologically confirmed NSCLC cT4 cN0/1 cM0 [cN0 in 34 and cN1 in 12 cases] underwent _ccRTx/CTx after induction chemotherapy (_iCTx). Median follow-up was 133 months. OS-rates at 3-, 5-, and 7-years were 74.9%, 57.4%, and 57.4%, respectively. Absolute OS-rate of _ccRTx/CTx at 5 years were within 10% of the trimodality treatment reference group (Log-Rank p = 0.184). The cumulative incidence of loco-regional relapse was higher after _iCTx + _ccRT/CTx (15.2% vs. 0% at 3 years, p = 0.0012, Gray’s test) while non-cancer deaths in the first year were lower than in the trimodality reference group (0% vs 9.1%, p = 0.0360, Gray’s test). None of the multiple recorded prognostic parameters were significantly associated with survival after _iCTx + _ccRT/CTx: Propensity score weighting for adjustment of prognostic factors between _iCTx + _ccRT/CTx and trimodality treatment did not change the results of the comparisons. Conclusions: Patients with cT4 N0/1 M0 NSCLC have comparable OS with _ccRTx/CTx and trimodality treatment. Loco-regional relapses were higher and non-cancer related deaths lower with _ccRTx/CTx. Definitive radiochemotherapy is an adequate alternative for patients with an increased risk of surgery-related morbidity.