Head and neck cancer (HNC) patients suffer from a range of health‐related quality of life (HRQoL) issues, but little is known about their long‐term HRQoL. This study explored associations between treatment group and HRQoL at least 5 years' post‐diagnosis in HNC survivors. In an international cross‐sectional study, HNC survivors completed the European Organization for Research and Treatment of Cancer (EORTC) quality of life core questionnaire (EORTC‐QLQ‐C30) and its HNC module (EORTC‐QLQ‐H&N35). Meaningful HRQoL differences were examined between five treatment groups: (a) surgery, (b) radiotherapy, (c) chemo‐radiotherapy, (d) radiotherapy ± chemotherapy and neck dissection and (e) any other surgery (meaning any tumour surgery that is not a neck dissection) and radiotherapy ± chemotherapy. Twenty‐six sites in 11 countries enrolled 1105 survivors. They had a median time since diagnosis of 8 years, a mean age of 66 years and 71% were male. After adjusting for age, sex, tumour site and UICC stage, there was evidence for meaningful differences (10 points or more) in HRQoL between treatment groups in seven domains (Fatigue, Mouth Pain, Swallowing, Senses, Opening Mouth, Dry Mouth and Sticky Saliva). Survivors who had single‐modality treatment had better or equal HRQoL in every domain compared to survivors with multimodal treatment, with the largest differences for Dry Mouth and Sticky Saliva. For Global Quality of Life, Physical and Social Functioning, Constipation, Dyspnoea and Financial Difficulties, at least some treatment groups had better outcomes compared to a general population. Our data suggest that multimodal treatment is associated with worse HRQoL in the long‐term compared to single modality.