Oral mucosa graft urethroplasty (OMGU) is a surgical technique used in complex hypospadias repair. However, long-term outcomes in prepubertal boys, particularly through and after puberty, are not well established. To systematically review the long-term outcomes of OMGU in prepubertal boys with hypospadias, focusing on changes observed after puberty. A systematic literature search was conducted in PubMed, Embase, and Cochrane Library. Studies reporting long-term outcomes of OMGU in prepubertal boys with hypospadias were included. The quality of evidence was assessed using the ROBINS-I tool. Three studies of moderate quality met the inclusion criteria. Outcomes were mixed, with some patients experiencing favorable results and others facing complications such as meatal stenosis, urethral strictures, and fistulas. The scarcity of high-quality, long-term studies highlights a significant knowledge gap in this area. This systematic review reveals insufficient evidence to establish the long-term efficacy and safety of OMGU in prepubertal boys with hypospadias, particularly concerning pubertal development and post-pubertal outcomes. Future research should prioritize prospective, longitudinal studies with larger sample sizes and standardized outcome measures to address these critical gaps in understanding.