Venous thromboembolism (VTE), commonly occurring in patients with testicular germ cell tumors (GCTs), is associated with increased morbidity and mortality. Prophylactic anticoagulation has been shown to decrease the risk of VTE in patients with malignancies. The objective was to evaluate the effect of low-molecular-weight heparin (LMWH) prophylaxis on the incidence of VTE and outcome in patients with GCT treated with first-line chemotherapy. In this retrospective study, 353 chemotherapy-naive GCT patients were treated with first-line chemotherapy at the National Cancer Institute, Bratislava, Slovakia (2000-2017). Median follow-up was 71 months. VTE was defined as any venous thrombosis or pulmonary embolism, confirmed by imaging, occurring during first-line chemotherapy. Exclusion criteria were LMWH use before starting chemotherapy and VTE on initial staging. We observed 14 (4.0%) VTE events. No visceral thromboses were observed. The difference in VTE incidence between patients with and without prophylaxis was not statistically significant (5.8% vs. 3.2%, p=0.37). We observed a trend toward longer overall survival in patients without prophylaxis (hazard ratio = 0.61, 95% confidence interval = 0.32-1.13, p=0.08). Patients with extragonadal GCT receiving VTE prophylaxis had significantly shorter survival (hazard ratio = 0.29, 95% confidence interval = 0.08-1.12, p=0.04). This effect was most likely driven by a higher incidence of treatment-related deaths in patients with extragonadal GCT receiving LMWH (p=0.06). LMWH prophylaxis was not associated with decreased VTE incidence. Moreover, there was a higher incidence of treatment-related deaths in patients with extragonadal tumor location. Low-molecular-weight heparin prophylaxis during hospitalization should not be used routinely in patients with testicular germ cell tumors receiving chemotherapy.