Background/Objectives: Prophylactic mastectomy can significantly reduce the risk of breast cancer in patients carrying gene mutations such as BRCA1 and BRCA2. Patients who opt for breast removal are offered tailored reconstructive options based on their medical history and prior treatments, and in these often young patients with limited autologous tissue reserves, implant-based reconstruction is frequently the option of choice. Complication rates of these procedures are relatively high and account for up to 30%. Subcutaneous mastectomy with primary implant reconstruction carries risks such as hematoma, seroma, skin necrosis, necrosis of the nipple–areola complex, and wound healing issues, which may necessitate revision surgery. This university-center retrospective analysis aims to improve outcomes by identifying patient- and surgery-related risk factors associated with postoperative complications in allogenic breast reconstruction following subcutaneous mastectomy. Methods: We analyzed 61 female patients and 122 breasts who underwent primary implant-based reconstruction after skin- or nipple-sparing subcutaneous mastectomy over three years between January 2021 and December 2023. Demographic and surgical variables were systematically collected and analyzed. Results: The mean patient age was 41.5 ± 10.3 years. A total of 13% of patients were active smokers, and 1.6% had diabetes mellitus. Overall, skin flap necrosis occurred in 27.9% of patients (22.1% of breasts), wound healing disorders in 19.7% of patients, wound infections in 9.8%, and revision surgery in 18.0%. A history of pregnancy was associated with skin flap necrosis (OR 10.07, 95% CI 1.79–190.06; p = 0.032); however, this finding must be interpreted with caution due to limited statistical power and model instability. Conclusions: This investigation revealed clinically relevant patterns suggesting potential risk factors for wound healing disorders and skin necrosis. Prospective studies are planned to further substantiate these findings and to help reduce overall complication rates associated with the procedure.