It is widely recognized in modern times that patients with malignant tumors originating in one testicle develop equally malignant tumors in the contralateral testicle. The incidence of testicular tumors is extremely low, about 1 in 50,000. Of the testicular malignancies that occur, the incidence of contralateral testicular tumors ranges from 1.2% to 5.8%. It is thought that the application of platinum-containing chemotherapy regimens in the last decade has led to increased cure rates and prolonged survival of testicular tumors, resulting in a tendency to increase the incidence of second primary testicular tumors. In concurrent or non-concurrent bilateral testicular tumors, the pathological type is predominantly spermatogonia, while other germ cell tumors are rare. Non-concurrent bilateral testicular tumors all develop at an older age, with 81.8% of patients occurring over 45 years of age, which may be related to the fact that patients with seminomatous cell tumors are easily cured by radiation therapy or chemotherapy and have prolonged survival. Cryptorchidism in the abdomen or groin is one of the risk factors for the development of testicular tumors. When the contralateral testis is enlarged, the possibility of a second primary testicular tumor must be considered and pathological examination must be done to clarify the histological type for further treatment. Treatment and prognosis are mainly related to clinical stage and histological type, and not related to whether the patient has a double primary testicular tumor per se. In patients with concurrent bilateral testicular seminoma, combined mediastinal left supraclavicular lymph node and systemic metastasis, the prognosis is poor; therefore, the treatment options for bilateral testicular tumors and the treatment principles for primary malignant tumors of the testis.