Background: Implant loss is the most severe complication of implant-based breast reconstructions. This study aimed to evaluate the incidence of implant loss and other complications, identify associated risk factors, and create a risk model for implant loss. Methods: This was a retrospective cohort study of all patients who underwent a mastectomy, followed by either a two-stage or a direct-to-implant breast reconstruction. Patient variables, operative characteristics, and postoperative complications were obtained from the patient records. A multivariate mixed-effects logistic regression model was used to create a risk model for implant loss. Results: A total of 297 implant-based breast reconstructions were evaluated. Overall, the incidence of implant loss was 11.8%. Six risk factors were significantly associated with implant loss: obesity, a bra cup size larger than C, active smoking status, a nipple-preserving procedure, a direct-to-implant reconstruction, and a lower surgeon's volume. A risk model for implant loss was created, showing a predicted risk of 8.4%-13% in the presence of one risk factor, 21.9%-32.5% in the presence of two, 47.5%-59.3% in the presence of three, and over 78.2% in the presence of four risk factors. Conclusions: The incidence of implant loss in this study was 11.8%. Six associated significant risk factors were identified. Our risk model for implant loss revealed that the predicted risk increased over 78.2% when four risk factors were present. This risk model can be used to better inform patients and decrease the risk of implant loss by optimizing surgery using personalized therapy.