Recent reports have suggested that nipple-sparing mastectomy (NSM) is a potential alternative to mastectomy (MT). The aim of our study was to investigate the oncological and technical outcomes of NSM compared with MT using long-term follow-up data. A total of 932 patients between April 1985 and March 2004 were enrolled in our study. Among them, 788 patients received NSM, whereas 144 patients received the routine mastectomy. The median follow-up time was 78 months. No significant difference in the probability of local recurrence between the NSM cohort and the MT cohort was found (8.2 vs. 7.6 %, p = 0.81). The rate of nipple-areola complex (NAC) relapse was low (3.7 %), and all of the nipple and/or areola recurrence cases were treated with NAC removal. Furthermore, nipple and/or areola recurrence was associated with a significantly better prognosis than that of skin flap recurrences and local lymph node recurrences. For the 21-year disease-free survival and the 21-year overall survival, no significant difference between the NSM and MT cohorts was observed. There was no occurrence of nipple necrosis in our trial. This was the first study to investigate the long-term follow-up of NSM in a large Japanese population. We reported the NSM could be performed without nipple necrosis and is oncologically as safe as mastectomy without radiotherapy. Therefore, we suggest that NSM without radiotherapy is a potential alternative to mastectomy for breast cancer patients for both outcome and aesthetic benefits.