Background: The EXTREME regimen (cetuximab with cisplatin/carboplatin and 5-fluorouracil) has long been a standard first-line treatment for recurrent and/or metastatic head and neck squamous cell carcinoma (R/M HNSCC), particularly in patients ineligible for immunotherapy. However, real-world evidence remains limited, especially in regions with delayed access to novel therapies. Methods: We conducted a retrospective, multicenter study of 217 patients with R/M HNSCC treated with cetuximab-based chemotherapy at six Croatian oncology centers between 2016 and 2022, prior to reimbursement of pembrolizumab. The primary endpoint was overall survival (OS); secondary endpoints included progression-free survival (PFS), response rates, and safety. Results: The majority (91%) received the EXTREME regimen. Median OS was 14 months (95% CI, 12–17), and median PFS was 6.2 months (95% CI, 6.0–7.2). Objective response rate was 21%, and disease control rate was 63%. Cetuximab-induced rash correlated with longer PFS. Grade ≥ 3 toxicity occurred in 18.9% of patients. No treatment-related deaths were observed. Conclusion: In routine clinical practice, cetuximab combined with platinum-based chemotherapy remains an effective and well-tolerated first-line treatment for R/M HNSCC, particularly in patients who are ineligible for immunotherapy or with PD-L1–negative tumors. These findings support its continued use in appropriately selected patients.