Objective: A subgroup of patients with an implantable cardioverter defibrillator (ICD) experiences anxiety after device implantation. The purpose of the present study was to evaluate whether anxiety is predictive of ventricular arrhythmias and all-cause mortality 1 year post ICD implantation. Methods: A total of 1012 patients completed the state version of the State-Trait Anxiety Inventory at baseline. The end points were ventricular arrhythmias and mortality the first year after ICD implantation. Results: Within the first year after ICD implantation, 19% of patients experienced a ventricular arrhythmia, and 4% died. Anxiety was associated with an increased risk of ventricular arrhythmias (hazard ratio [HR] = 1.017; 95% confidence interval [CI] = 1.005-1.028; p = .005) and mortality (HR = 1.038; 95% CI = 1.014-1.063; p = .002) in adjusted analysis. Patients with anxiety (highest tertile) had a 1.9 increased risk for ventricular arrhythmias (95% CI = 1.329-2.753; p = .001) and a 2.9 increased risk for mortality (95% CI = 1.269-6.677; p = .01) compared with patients with low anxiety (lowest tertile). Among 257 patients with cardiac resynchronization therapy, anxiety was associated with mortality (HR = 5.381; 95% CI = 1.254-23.092; p = .02) after adjusting for demographic and clinical covariates. Conclusions: Anxiety was associated with an increased risk of ventricular arrhythmias and mortality 1 year after ICD implantation, independent of demographic and clinical covariates. Monitoring and treatment of anxiety may be warranted in a selected subgroup of high-risk patients with an ICD.