The aim of this study was to investigate the effect of C-reactive protein (CRP) level on the prognosis of patients with locoregionally advanced laryngeal carcinoma treated with chemoradiotherapy. Fifty-seven patients with locoregionally advanced laryngeal carcinoma (cT3-4, N0-3, M0) treated with chemoradiotherapy were reviewed retrospectively. Chemoradiotherapy comprised external beam radiotherapy to the larynx (70 Gy) with three cycles of cisplatin at 3-week intervals. Elevated CRP was defined as >8 mg/L. The survival rate was calculated using the Kaplan-Meier method, and a multivariate analysis was used to identify significant factors associated with prognosis, using a Cox proportional hazards model. During the median (range) follow-up of 5 years (1.3-5), 29 patients died from laryngeal cancer; the 5-year cancer-specific survival (CSS) rate was 49.12%. Fifteen patients had a high CRP level before chemoradiotherapy (>8 mg/L), and their CSS rate was significantly worse than that in the remaining patients (P = 0.003). Multivariate analysis showed that CRP and tumor site were independent prognostic indicators for CSS, with a hazard ratio of 2.66 (95% confidence interval (CI), 1.22-5.82; P = 0.014) and a hazard ratio of 1.67 (95% CI, 1.01-2.77; P = 0.045), respectively. Of those with elevated CRP, the CRP levels of ten patients became normal after chemoradiotherapy, of whom four were alive with no evidence of recurrence or metastasis during the follow-up. By contrast, all six with no CRP normalization after chemoradiotherapy died within 3.8 years. The elevation of CRP before treatment predicts a poor prognosis in patients with locoregionally advanced laryngeal carcinoma treated with chemoradiotherapy.