Seminomas are most commonly diagnosed in clinical stage I (CSI). After orchiectomy, approximately 15% of patients in this stage have subclinical metastases. Adjuvant radiotherapy (ART) delivered to the retroperitoneum and ipsilateral pelvic lymph nodes has been the mainstay of treatment for many years. Although highly efficient, with long-term cancer-specific survival (CSS) rates approaching almost 100%, ART is associated with considerable long-term consequences, particularly cardiovascular toxicity and increased risk of secondary malignancies (SMN). Therefore, active surveillance (AS) and adjuvant chemotherapy (ACT) were developed as alternative treatment options. While AS prevents patient overtreatment, it is associated with strict follow-up regimens and increased radiation exposure due to repeated imaging. Due to equivalent CSS rates to ART, and lower toxicity, one course of adjuvant carboplatin presents the cornerstone of chemotherapy for CSI patients. CSS is almost 100% for patients with CSI seminoma, regardless of the chosen treatment option. Therefore, a personalized approach in treatment selection is preferred. Currently, routine radiotherapy for CSI seminoma patients is no longer recommended. Instead, it should be reserved for patients who are unfit or unwilling for AS or ACT. Identification of prognostic factors for disease relapse allowed for the development of risk-adapted treatment strategy and stratification of patients in low-risk and high-risk groups. Although risk-adapted policy needs further validation, surveillance is currently recommended in low-risk patients, while ACT is reserved for patients with a higher risk of relapse.