Venous thromboembolism (VTE) is associated with inferior survival in cancer patients. The risk of VTE and its effect on survival in chronic lymphocytic leukemia (CLL) patients remains unclear. The present study investigated the impact of patient-related factors, CLL prognostic markers, and CLL treatment on the risk of VTE and assessed overall survival relative to VTE. All patients in the Danish National CLL Registry (2008-2015) were followed from the date of CLL diagnosis to death, VTE, emigration, or administrative censoring. Hazard ratios (HRs) were estimated using Cox models, and second primary cancers and anticoagulation treatment were included as time-varying exposures. During a median follow-up of 2.6 years, 92 VTEs occurred among 3609 CLL patients, corresponding to a total incidence rate of 8.2 VTEs per 1000 person-years (95% confidence interval [CI], 6.7-10.1). A history of VTE or second primary cancer was associated with HRs of VTE of 5.09 (95% CI, 2.82-9.17) and 3.72 (95% CI, 2.15-6.34), respectively, while b 2-microglobulin .4 mg/L, unmutated immunoglobulin HV and unfavorable cytogenetics had lower HRs. CLL patients with VTE had marginally higher mortality, which was most pronounced among patients,60 years of age (HR, 7.74; 95% CI, 2.12-28.29). Our findings suggest that markers of unfavorable CLL prognosis contribute to an increased risk of VTE; however, previous VTE or a second primary cancer is more strongly associated with the risk of VTE than any CLL-specific marker. Focusing attention on this preventable complication may improve survival in young CLL patients.