Background: Primary amenorrhoea (PA) is defined as the lack of menstruation at age 13 years in the absence of normal growth and secondary sexual characteristics, or lack of menstruation at age 15 years in the setting of normal growth and secondary sexual characteristics. Most underlying causes of PA can be classified into gonadal, anatomic, endocrine and systemic causes. Disorders of sexual development (DSD) are a rare, yet challenging aetiology. Case description: We present a 24-year-old, previously healthy female, who complained of PA and absent breast development. The patient denied any other symptoms. The physical examination revealed a tall girl, with infantile breasts and unambiguous female external genitalia, with no abnormalities. Laboratory tests showed hypogonadotropic hypogonadism (HH), undetectable anti Müllerian hormone (AMH), present Müllerian structures and absent ovaries in the pelvic magnetic resonance imaging (MRI), with a 46,XY karyotype. The abdominal and pelvic laparoscopy confirmed the presence of Müllerian structures, with no evidence of gonadal tissues. A diagnosis of early testicular regression syndrome (ETRS) was given. Hormonal replacement therapy (HRT) was started and escalated thereafter, resulting in regular menses, breast development and patient satisfaction. Conclusion: PA in a 46,XY female is a challenging disorder. Although several differential diagnoses are considered, the unique clinical, hormonal, radiological and cytogenic findings are helpful in suggesting the diagnosis of ETRS.