Introduction: As an acute-phase protein synthesized in response to systemic inflammation, the C-reactive protein (CRP) has been shown to be an independent prognostic factor for patients with castration-resistant prostate cancer (CRPC). The aim of this study was to investigate the association between CRP and progression-free survival (PFS), overall survival (OS) and radiological response in CRPC patients treated with docetaxel. Methods: 115 histologically confirmed CRPC patients who were treated with docetaxel chemotherapy from 2008 to 2013 were selected. Univariable and multivariable Cox regression models were used to predict the association of CRP as a dichotomous variable with PFS and OS after chemotherapy initiation. Results: None of the clinicopathological features were associated with the CRP. In Kaplan-Meier analysis, the median PFS (9.8 vs. 7.5 months, p < 0.001) and OS (26.5 vs. 13.5 months, p = 0.002) were higher in patients who did not have an elevated CRP than in those with an elevated CRP. In univariable analysis, the pretreatment CRP was significantly associated with PFS (p < 0.001) and OS (p = 0.003).In multivariable analysis, patients with a CRP > 8 mg/l were at significantly higher risk of tumor progress (hazard ratio (HR) 2.184; 95% confidence interval (CI) 1.401-3.403; p = 0.001) and death (HR 2.003; 95% CI 1.285-3.121; p = 0.002) than patients with a CRP ≤ 8 mg/l. Conclusions: CRP may be an important biomarker of PFS and OS in CRPC patients treated with docetaxel. The findings require validation in further prospective, large cohort-size studies.