The aim of this study was to comprehensively evaluate via a meta-analysis the association between p27 expression and clinical outcome in breast cancer patients. We conducted a meta-analysis of 20 studies (n= 6463 patients) that evaluated the correlation between p27 expression and indicators of breast cancer clinical outcome, including overall survival (OS), disease-free survival (DFS) and relapse-free survival (RFS). Data pooling was performed by RevMan 4.2. A total of 60% (9 of 15) of the studies showed a significant association between p27 high expression and OS, whereas 25% (2 of 8) and 60% (3 of 5) studies demonstrated a correlation between p27 high expression and DFS and RFS, respectively. The relative risks (RRs) were 1.34 (1.26-1.42) for OS (P < 0.00001), 1.27 (1.10-1.47) for DFS (P= 0.001) and 1.49 (0.92-2.42) for RFS (P= 0.10). In lymph node-negative breast cancer patients, the RRs for OS and RFS were 1.84 (1.30-2.59; P= 0.0005) and 1.30 (0.20-8.50; P= 0.78), respectively. In lymph node-positive breast cancer patients, the RRs for OS and RFS were 2.99 (1.77-5.07; P < 0.0001) and 1.49 (0.80-2.77; P= 0.21), respectively. This meta-analysis indicates that reduced p27 is an independent prognostic factor for poor overall and disease-free cancer survival.