BACKGROUND: Mastectomy is performed in female-to-male transsexual (FTM TS) patients as a surgical treatment to make a female thorax resemble a male thorax; however, no studies have examined the nipple-areolar complex (NAC) position in FTM TS patients after mastectomy. PATIENTS AND METHODS: The NAC position in 41 FTM TS patients before and after non-skin-excisional mastectomy was examined and compared with that in 50 age- and BMI-matched biologically male subjects as controls. The factors affecting the NAC position after the operation were also examined and verified by multiple regression analysis. RESULTS AND CONCLUSIONS: After non-skin-excisional mastectomy, the NAC in the FTM TS patients was positioned significantly more medially (horizontal NAC position ratio {('internipple distance'/'width of thorax') × 100} [HNPR]: preoperatively, 70.07% ± 4.19%; postoperatively, 63.28% ± 3.79%) and cranially (vertical NAC position ratio {('distance from sternal notch to nipple height'/'distance from sternal notch to umbilicus') × 100} [VNPR]: preoperatively, 43.87% ± 3.68%; postoperatively, 41.37% ± 3.15%). Postoperatively, the NAC in the FTM TS patients was located significantly more medially than that in the control subjects (HNPR: 63.28% ± 3.79% to 66.79% ± 4.82%), although the height of the NAC was the same. Multiple regression analysis revealed that the NAC position on breasts characterized by ptosis, a high projection, and lateral leaning (low skin elasticity and a substantial amount of skin between the nipples) tended to be positioned more medially after non-skin-excisional mastectomy. Laterally deviated eccentric circular type mastectomy may be a good option for FTM TS patients who have moderately sized breasts with such features. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .