Phalloplasty is performed as genital gender-affirming surgery in transmasculine persons. It requires the harvest of sizeable autologous fasciocutaneous flaps, which is associated with donor-site morbidity and extensive scarring. Flap preexpansion has been used to facilitate wound closure and reduce scarring, but the efficacy of flap preexpansion in phalloplasty is unclear. The objective of this study was to assess the safety and effectiveness of preexpansion before phalloplasty.