BACKGROUND : In immediate one-stage implant-based breast reconstruction, acellular dermal matrix (ADM) is widely used around the world due to its ability to cover the outside part of the pectoralis major muscle. Unfortunately, ADM has not yet been approved in Japan. Consequently, in our institution, we have performed safe one-stage implant-based breast reconstruction without ADM by employing several unique techniques and have obtained excellent results. METHODS : The data of 186 patients were reviewed. In each case, we performed three unique steps to determine which cases were suitable for one-stage implant-based breast reconstruction as follows. First, ICG fluorescence imaging was performed to confirm the blood flow of the skin after mastectomy. Next, a serratus anterior muscle/fascial and external oblique fascial flap was elevated to completely cover the implant together with the pectoralis major muscle. We used a sizer to confirm the skin tension and the form of the breast. After confirming correct size, shape and coverage, we selected cases in which implant could be safely performed. We evaluated the final cosmetic outcome based on three measurements: the inframammary fold position, and the bilateral balance of both breast size and form. RESULTS : The rate of immediate one-stage implant-based reconstruction was 85.7%. An implant was removed in one case because of complications, and infection developed in five cases. Among all patients, the overall cosmetic evaluation of the final outcome was evaluated as good, fair and poor in 84.3%, 13.5% and 2.2% of cases, respectively. CONCLUSIONS : Immediate one-stage implant-based breast reconstruction without ADM can be a useful and safe procedure, based on our unique techniques in breast cancer patients who hope for immediate prosthetic breast reconstruction in Japan.