Following orchiectomy, patients with clinical stage I (CSI) testicular seminoma may be managed by active surveillance (S) or adjuvant treatment (radiotherapy or chemotherapy). In view of the published data on long-term toxicity, especially second malignant neoplasms (SMNs), adjuvant radiotherapy (ART) is currently no longer recommended as an adjuvant therapy option for these patients. The purpose of our recent study was to compare the impact of two selected treatment approaches-S versus adjuvant chemotherapy (ACT) on the survival of patients with CSI testicular seminoma. This cross-sectional study analyzed a total of 139 patients collected at a single center between 10/2011-5/2020, with CSI testicular seminoma, stratified into two groups according to risk-adapted therapeutic approaches. In the S group (low-risk-without rete testis invasion-RTI, primary tumor size < 4 cm), consisting of 77 patients, who underwent S, relapse occurred in 10 (13.0%) patients after a mean follow-up of 14.3 months. In the ACT group (high-risk-RTI and/or primary tumor size > 4 cm), consisting of 62 patients, who were treated with ACT, relapse occurred in 5 (8.1%) patients after a mean follow-up of 11.6 months. Overall survival of patients in both groups was 100% with a mean follow-up of 43.9 months. A statistically significant difference in progression-free survival (PFS) between these two groups was not found. Based on our findings, ACT seems to be an adequate treatment for patients with a high-risk of relapse, as well as S for those with a low-risk of relapse. Despite its excellent prognosis, optimal management of CSI testicular seminoma remains controversial, with variations in expert opinion and international guidelines.