Objective: To summarize the ultrasonographic characteristics of testicular adrenal tumor (TART) in male patients with congenital adrenocortical hyperplasia (CAH) due to 21-hydroxylase deficiency, and to improve the understanding of sonographers on TART. Methods: Twenty-one CAH patients due to 21-hydroxylase deficiency were collected. All patients were found to have abnormal echoes in the testis by scrotal high-frequency ultrasound examination and were diagnosed as TART. The ultrasonic images of TART lesions were observed, and the number and growth mode of the lesions involving the testis were evaluated. The morphology, boundary, echogenicity and blood supply characteristics, and epididymis involvement were observed. Results: Among the 21 patients, 14 patients had bilateral testicular lesions with the same ultrasound features, and seven patients were unilateral. Two patients were epididymal involvement. Among the total 35 testicular lesions, 82.9% (29/35) grew along the testicular mediastinum, 17.1% (6/35) grew diffusely. Hypoechoic lesions accounted for 51.4% (18/35), heterogeneous hyperechoic lesions accounted for 28.6% (10/35), and heterogeneous hyperechoic lesions with coarse calcification accounted for 20%(7/35). The lesion morphology mainly showed irregular lobular shape and round shape, accounting for 85.7% (30/35) and 14.3% (7/35), respectively. The rich blood supply lesions accounted for 62.8% (22/35), and 22.9% (8/35) and 14.3% (5/35) of the lesions were hypovascular or anvascular. Conclusions: Sonographic appearance of TART is variable but still characteristic. The lesions present as bilateral testis with rich blood supply and irregular hypoechoic growth along the mediastinum. The ultrasonic features of the bilateral lesions are the same. With the history of CAH, it might provide clues for diagnosis of TART.