Objective:To explore whether botulinum toxin A (BTX-A) can improve the retention rate of fat transplantation in fat breast augmentation.Methods:Each patient was divided into control side and experimental side according to the random number table in 14 patients studied. The experimental group received autologous fat and BTX-A combined transplantation on both sides of the breast, while the control side only received autologous fat transplantation. The fat was added with the same volume of normal saline as BTX-A in the control group. All patients were followed up and the effects of BTX-A were evaluated objectively via the comparison of the remained bilateral fat graft volumes that were obtained through a digital three-dimensional reconstructions technique. Moreover, the improvement of each breast appearance and complication were assessed by the physician and patients who were blinded to the recipient treatment assignment.Results:The outcome of the fat breast augmentation was evident for both groups at the follow-up with no evidence of fat embolism, vascular/nervous injury, infection and prolonged bruising. In one of the 14 patients (control group), fat liquefaction necrosis occurred in one side of the breast; after active treatment, it returned to normal, and three patients had different degrees of mass. The analysis on the three-dimensional reconstruction data and the assessments from both the physicians and patients showed significant differences in the fat graft retention volume between the BTX-A group (51.10±20.56)% and the control group (33.06±14.77)%. Nevertheless, there was no significant difference in the incidence of complications between the two sides.Conclusions:Autogenous fat breast augmentation is safe and effective. This study result has shown that BTX-A can significantly improve the retention rate of fat transplantation but cannot reduce the incidence of complications.