Background: Testicular adrenal rest tumours (TARTs) are benign testicular masses that are found in inadequately treated patients with congenital adrenal hyperplasia (CAH). Recognizing this association and identifying characteristic ultrasound features of TARTs is important so as to avoid misdiagnosing them as malignancies, which can lead to unnecessary interventions. Case Report: We describe a case of a 9-year-old boy, with a diagnosis of CAH and precocious puberty, who was referred to our department for an ultrasound evaluation of the abdomen and scrotum. On ultrasound, there were well-defined, heterogeneous, predominantly hypoechoic, round-to-oval masses in both testes. Taking into account the presence of CAH and a typical sonographic appearance of bilateral testicular masses, a diagnosis of testicular adrenal rest tumour was made; biopsy was deferred and hormonal treatment was modified. Conclusions: Prompt diagnosis of testicular adrenal rest tumours is essential, as it only indicates inadequate hormonal control. Moreover, it can prevent unnecessary biopsies and orchidectomies, and can maintain fertility. TARTs have a typical imaging appearance that every radiologist must be aware of.