BACKGROUND: Although immune checkpoint inhibitors (ICIs) are approved for the treatment of recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC), the response to ICIs remains unclear. AIMS/OBJECTIVES: To summarize the clinical outcomes of patients with HNSCC treated with nivolumab (Nivo) in our institution, and provide a basis for research on biomarkers that can predict the efficacy of ICIs. MATERIAL AND METHODS: Forty-four patients with R/M HNSCC who received Nivo (2017-2022) were retrospectively analysed. RESULTS: Despite the older age of this cohort (median age of 72 years), we observed favourable long-term outcomes, with an overall survival of 24.1 months, which could be attributed to our aggressive nutritional intervention. Older age, poor performance status (≥1), and higher Glasgow Prognostic Scores, reflecting the chronic inflammation and malnutrition of patients, were associated with poor prognoses, with hazard ratios for death of 2.63 (95% confidence interval [CI]; 1.07-6.46,  = .016), 3.50 (95% CI; 1.28-9.55,  = .001), and 2.69 (95% CI; 1.17-6.21,  = .029), respectively. Peripheral blood biomarker analysis revealed that systemic inflammation may negatively affect the efficacy of Nivo. CONCLUSIONS AND SIGNIFICANCE: Our results suggest that nutrition and inflammation must be the focus of future studies aiming to identify novel biomarkers.