BACKGROUND:The objective of this study was to determine whether fertility preservation (FP) with oocyte/embryo cryopreservation is associated with differences in disease-free survival (DFS). METHODS: This retrospective study included patients aged 18 to 45 who were diagnosed with invasive breast cancer between 2007 and 2017 and were seen for FP consultation at a university fertility center before cancer treatment. The primary endpoint, DFS, was defined as the time from FP consultation until patients developed a locoregional recurrence, distant metastasis, a contralateral breast tumor, or a new primary malignancy. DFS was compared for FP versus no FP using Kaplan-Meier survival estimates and Cox proportional-hazard regression analysis. RESULTS: The study included 329 women, with 207 (63%) in the FP group and 122 (37%) in the no FP group. Patients who underwent FP had more aggressive initial disease profiles than those in the no FP group. In addition, they were younger (35 vs 37 years; P = .009), more often had stage II or III disease (67% vs 55%; P = .03), and had higher rates of requiring chemotherapy (77% vs 65%; P = .01). Over a median follow-up of 43 months, the rates of DFS were similar among patients in the FP group and the no FP group (93% vs 94%, respectively; hazard ratio [HR] 0.7; 95% CI, 0.3-1.7). Positive ER status (79% vs 83%; P = .38), neoadjuvant chemotherapy (41% vs 48%; P = .32), ER-positive DFS (HR, 0.4; 95% CI, 0.1-1.6), and neoadjuvant chemotherapy DFS (HR, 1.4; 95% CI, 0.2-9.1) were similar in the FP and no FP groups, respectively. CONCLUSIONS: At a median follow-up of 43 months, FP appears unlikely to affect DFS, even in the setting of tumors with positive ER status or treatment with neoadjuvant chemotherapy (in which the tumor remains in situ during FP). Cancer 2020;126:487-495.