46, XX testicular disorder is a rare disorder characterized by karyotype analysis being 46,XX in an individual whose phenotype is male. Gynecomastia after puberty, small testes and sterility due to azoospermia may occur, but penile length and pubic hair are usually normal. In rare cases, inadequate virilization of the external genitalia; hypospadias, undescended testis, or ambigius genitalia could be seen. Short stature and normal mental development are other clinical features of 46, XX testicular disorder. A 13 1/2 old male patient presented to our outpatient clinic with the complaint of gynaecomastia. İn the physical examination revealed that short stature (10th percentile), gynecomastia and small testes. On laboratory examination, LH: 24.32 mIU / ml, FSH: 34.26 mIU / ml, Estradiol: 34.53 pg / ml, Total Testosterone: 1.62 ng / ml, after this results karyotype analysis was performed and reported as 46 XX. With positive SRY gene analysis, the patient was diagnosed with 46, XX testicular sexual development disorder. This case is presented to emphasize the importance of chromosome analysis when hypergonadotropic hipogonadism is detected in patients presenting with gynecomastia during puberty.