This study aimed to explore the clinical and oncologic findings in patients with de novo metastatic prostate cancer (mPCa) and extraprostatic extension (EPE) on biopsy. We retrospectively evaluated data on 630 patients with de novo mPCa between January 2009 and December 2017 in the West China Hospital (Chengdu, China), including evaluating the relationships between EPE and other variables and the association of EPE with survival outcomes by the Chi-square test, Kaplan-Meier curves, and the Cox proportional-hazards model. EPE was found in 70/630 patients, making a prevalence of 11.1%. The presence of EPE on biopsy was associated with higher Gleason scores and higher incidence of neuroendocrine differentiation (NED), intraductal carcinoma of the prostate (IDC-P), and perineural invasion (PNI). Compared with those without EPE, patients with EPE had shorter castration-resistant prostate cancer-free survival (CFS; median: 14.1 vs 17.1 months, P = 0.015) and overall survival (OS; median: 43.7 vs 68.3 months, P = 0.032). According to multivariate analysis, EPE was not an independent predictor for survival. Subgroup analyses demonstrated that patients with favorable characteristics, including negative NED or IDC-P status, Eastern Cooperative Oncology Group (ECOG) score <2, and prostate-specific antigen (PSA) <50 ng ml-1, had worse prognoses if EPE was detected. In patients with PSA <50 ng ml-1, EPE was a negative independent predictor for OS (hazard ratio [HR]: 4.239, 95% confidence interval [CI]: 1.218-14.756, P = 0.023). EPE was strongly associated with other aggressive clinicopathological features and poorer CFS and OS. These data suggest that EPE may be an indicator of poor prognosis, particularly in patients, otherwise considered likely to have favorable survival outcomes.