Objective To describe the incidence, clinical characteristics, treatment methods and long‐term follow‐up of bilateral germ cell tumours of the testis (GCTT) in patients treated at one institution. Patients and methods Of 552 patients with GCTT, 11 (2%, mean age 26.9 years) developed bilateral disease; all 11 underwent radical orchidectomy. Additional treatment was planned according to the histological type and clinical stage of the tumour, and previous treatments. Intramuscular testosterone was administered periodically after total castration. The data on survival, sexual status and treatment complications were reviewed. Results Of the 11 patients, seven developed a second tumour metachronously (median interval 87 months) and four had synchronous bilateral GCTT. Cryptorchidism, infertility or atrophic testis was associated with the development of bilateral GCTT in seven of the 11 patients. All synchronous tumours and most of the sequential tumours had identical histology on both sides. Although all sequential tumours presented at an early clinical stage, three of four synchronous bilateral GCTTs presented at an advanced stage. Five patients received platinum‐based chemotherapy; three patients underwent post‐ chemotherapy resection of the retroperitoneal residual mass. Sexual libido and potency were conserved in all patients. No significant morbidity was recorded as being caused by any of these treatments. At a median follow‐up of 11.6 years, all patients were alive with no evidence of cancer. Conclusions All patients with unilateral GCTT have an increased risk of developing a contralateral testicular tumour, even decades after diagnosis. Management should be adapted to each patient. As all patients in this series survived in the long‐term, developing a second germ cell cancer does not necessarily predict a poor prognosis.