Serum tumor markers have an important role in the management of patients with testicular cancer. They are useful for diagnosis, staging and risk assessment, follow-up, evaluation of response, and early detection of relapse. Alpha-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase are established serum markers in testicular cancer, but they have a limited sensitivity. Ongoing research may lead to the identification of novel biomarkers. Therefore, we review the experimental analyses for nucleic acids, circulating tumor cells, and proteins as potential biomarkers in the serum of testicular germ cell cancer patients.