BACKGROUND: Complete androgen insensitivity syndrome is caused by inactivated mutations in the androgen receptor gene, which results in complete androgen resistance and a female phenotype with a 46,XY karyotype. This condition is rare in twins. CASE PRESENTATION: We report on a Han Chinese twin girl, aged 18 years, with the presence of a vagina and breasts but no uterus and ovaries and chromosomal karyotype analysis showing 46, XY, who was diagnosed with complete androgen insensitivity syndrome. The patient underwent bilateral gonadectomy and hormone replacement therapy, and pathological diagnosis showed immature testicular tissue development. CONCLUSION: In addition to rebuilding the external genitalia and preventing the emergence of gonadal tumors, continuing hormone replacement therapy after surgery is critical for the treatment of complete androgen insensitivity syndrome, and patients' psychological difficulties should be addressed.