Background: The standard treatment for metastatic castration-resistant prostate cancer (MCRPC) is Docetaxel (DTX); however, it has serious adverse effects. It is necessary to know the prognostic factors for overall survival (OS) of patients with MCRPC treated with DTX. The aim of this study was to determine the prognostic factors for OS in patients with MCRPC treated with DTX. Methods: This study is a secondary analysis of the control arms of the clinical trials NTC00273338, NCT00519285 and NCT00988208. 1600 patients aged 18 years or older with MCPRC that received DTX and prednisone were included. Survival curves were estimated by Kaplan-Meier and comparison was done by log-rank test. Multivariate analysis for overall survival (OS) was performed with the Cox proportional hazard regression model. Results: The median OS time was 14.64 months. The 1-yr-OS and 2-yrs-OS were 86.2% and 28.6%, respectively. Patients with an ECOG score greater than 0 lived significantly less than the rest of patients (p = 0.00). The patients with an alkaline phosphate level (ALP) > 200 had significantly lower OS (p = 0.00). In the multivariate analysis, the factors that influenced OS were ECOG, ALP, HB, LDH and number of metastases. Conclusions: Poor performance status, high alkaline phosphatase level, low hemoglobin level, high LDH and more than 2 metastases were the main prognostic factors in patients with metastatic castration resistant prostate cancer. HR95% CIPECOG > 01.371.17-1.60.00ALP > 2001.831.54 - 2.150.00HB < 131.431.21-1.690.00LDH > 1931.231.01-1.490.036M > 21.341.09-1.630.004