OBJECTIVE To examine whether contralateral prophylactic mastectomy (CPM) is associated with improved survival, incidence of contralateral breast cancer (CBC), and recurrence in patients with unilateral breast cancer (UBC). BACKGROUND Despite conflicting data, CPM rates continue to increase. Here we present the first meta-analysis to assess post-CPM outcomes in women with UBC. METHODS We searched 5 databases and retrieved papers' bibliographies for relevant studies published through March 2012. Fixed- and random-effects meta-analyses were conducted on the basis of tests of study heterogeneity. We examined potential confounding via stratification and meta-regression. We report pooled relative risks (RRs) and risk differences (RDs) with 95% confidence intervals (CIs) at 2-tailed P < 0.05 significance. RESULTS Of 93 studies reviewed, 14 were included in meta-analyses. Compared with nonrecipients, CPM recipients had higher rates of overall survival [OS; RR = 1.09 (95% CI: 1.06, 1.11)] and lower rates of breast cancer-specific mortality [BCM; RR = 0.69 (95% CI: 0.56, 0.85)] but saw no absolute reduction in risk of metachronous CBC (MCBC). Among patients with elevated familial/genetic risk (FGR, ie, BRCA carrier status and/or family history of breast cancer), both relative and absolute risks of MCBC were significantly decreased among CPM recipients [RR = 0.04 (95% CI: 0.02, 0.09); RD = -24.0% (95% CI: -35.6%, -12.4%)], but there was no improvement in OS or BCM. CONCLUSIONS CPM is associated with decreased MCBC incidence but not improved survival among patients with elevated FGR. The superior outcomes observed when comparing CPM recipients with nonrecipients in the general population are likely not attributable to a CPM-derived decrease in MCBC incidence. UBC patients without known FGR should not be advised to undergo CPM.