Abstract Background Preexisting pulmonary hypertension (PH) is associated with unfavorable in-hospital outcomes in cardiac as well as non-cardiac surgeries and procedures. However, its impact on cardiac implantable electronic device (CIED) implantations is not established. We investigated the extent of preexisting PH among patients undergoing CIED implantations and evaluated its effect on in-hospital outcomes. Methods Using the National Inpatient Sample (NIS) database, we identified patients who were hospitalized in the US between 2016-2019 and underwent CIED implantation with a preexisting diagnosis of PH. Patients with any CIED in-situ were excluded. Sociodemographic, clinical data, in-hospital procedures and outcomes as well as in-hospital mortality were collected. Multivariable logistic regression models were used to identify predictors of in-hospital complications. Results An estimated total of 718,980 patients underwent CIED implantation during the study period. Of them, 74,150 patients (10.3%) had preexisting PH diagnosis. Compared with non-PH patients, PH patients were older, had higher Charlson Comorbidity Index, and more often implanted with implantable cardioverter defibrillators and cardiac resynchronization therapy devices. Higher rate of total complications was observed in PH patients (14.5% versus 9.9%; P<0.001) driven mainly by respiratory complications as well as in-hospital mortality (2.3% versus 1.2%; P<0.001). Multivariable analyses confirmed PH as an independent predictor for respiratory complications, total complications and in-hospital mortality. Conclusion Preexisting PH in patients undergoing CIED implantation was associated with increased risk for respiratory complications as well as in-hospital mortality in a US nationwide, all-comer registry.