To assess radiotherapy (RT) outcomes in patients with gingival carcinoma and growth up to or involvement of the lower jaw bone. This was aretrospective analysis of 51patients with squamous cell carcinomas of the gingiva. Patients received definitive (group1, 31.4%) or postoperative (group2, 66.7%) RT between 2005 and 2017 at the Department of Radiation Oncology, University Hospital Heidelberg. The primary endpoint was overall survival (OS) in both treatment groups. Other endpoints were local-disease-free survival (LDFS), progression-free survival (PFS) and treatment-related toxicity (Common Terminology Criteria for Adverse Events, CTCAE, Version4.03). Median age at first diagnosis was 63years. All patients had alocal advanced disease (American Joint Commission on Cancer [AJCC] stageIII-IV). After amedian follow-up of 22months (range 3-145months), 20patients (39.2%) were still alive. At 5years, OS rate was 36.6%. No significant differences in OS (p = 0.773), PFS (p = 0.350) and LDFS (p = 0.399) were observed between the two groups. Most common higher-grade acute RT-related complications (≥ grade3) were dermatitis (78.2%), oral mucositis (61.7%), xerostomia (51.5%), and loss of taste (74.6%). Three cases (5.8%) of osteoradionecrosis (ORN) of the lower jaw were detected after 15-31months. Definitive and postoperative RT have similar treatment outcomes for patients with lower gingiva carcinomas of the lower jaw. The most common acute complications (grade ≥3) were dermatitis, oral mucositis, xerostomia and loss of taste.