IMPORTANCE: Autologous fat transfer (AFT or fat grafting) has become an invaluable tool for the correction of disfiguring deformities after breast cancer surgery. However, clinical and animal studies have shown conflicting results regarding its oncologic safety. OBJECTIVE: To determine whether exposure to AFT vs conventional breast reconstruction is associated with increased rates of cancer relapse in patients with breast cancer. DESIGN, SETTING, AND PARTICIPANTS: This matched cohort study involved retrospective medical record review to identify all patients in a local patient database receiving AFT between 2006 and 2014. Each AFT case was matched with a nonexposed control patient with similar baseline characteristics. The mean (SD) follow-up of patients receiving AFT was 9.3 (4.9) years including 5.0 (1.7) years following AFT. Control patients were followed up for a mean (SD) of 8.6 (1.8) years from the primary surgery. Patients were identified through the local patient database of the Tergooi Hospital in Hilversum, the Netherlands. A total of 287 patients with breast cancer (300 affected breasts) who received AFT for breast reconstruction after cancer were included in the intervention group. Each AFT case was matched with a respective control patient based on age, type of oncologic surgery, tumor invasiveness, and disease stage. In addition, individual AFT-control pairs were selected to have the same locoregional recurrence-free interval at baseline. Data were analyzed between 2016 and 2017. EXPOSURES: Reconstruction with AFT vs conventional breast reconstruction or none. MAIN OUTCOMES AND MEASURES: Primary end points were the cumulative incidences of oncologic events in AFT and control patients and their respective hazard ratios. RESULTS: Of the 587 total patients, all were women and the mean age was 48.1 years for the patients undergoing AFT and 49.4 years for the control patients. Eight locoregional recurrences were observed in the treatment group (287 patients) and 11 among the control group (300 patients), leading to an unadjusted hazard ratio of 0.63 (95% CI, 0.25-1.60; P = .33). No increased locoregional recurrence rates were seen in relevant subgroups based on the type of oncological surgery, tumor invasiveness, or pathological stage. In addition, no increased risks with AFT were detected with respect to distant recurrences or breast cancer-specific mortality. CONCLUSIONS AND RELEVANCE: No significant differences in the locoregional recurrence rates between the AFT and control groups were observed after 5 years of follow-up. These findings confirm the results of previous studies; therefore, clinical evidence suggesting that AFT is associated with increased risk for cancer relapse is still lacking.