<h3>Purpose</h3> Pulmonary hypertension (PH) is associated with multiple comorbidities, cardiac structural changes and development of arrythmias. Atrial fibrillation is an independent risk factor in left sided heart disease. We sought to examine the prevalence, clinical manifestation and impact of AF on PH in a US National Inpatient Database. <h3>Methods</h3> This study is a retrospective analysis of National Inpatient Sample data, collected between 2005-2014. Patients ≥65 years of age, admitted with PH were included in the study. ICD-9 codes were used to identify both PH (416.0, 416.2, 416.8, 416.9) and AF (427.31) patients. The primary outcomes of the study were in-hospital mortality rate, hospital length of stay, and hospitalization cost. Propensity-score matching analysis was done to examine the effect of AF among PH patients on primary outcomes. <h3>Results</h3> There was a total of 5,428,332 patients admitted with PH, of which 2,897,257 (53.4%) had AF. Mortality rates (5.7% versus 4.8%, <i>P</i> <0.001), hospital length of stay (4.6 days versus 3.9 days, <i>P</i> <0.001), and hospitalization costs ($17,711versus $14,110, <i>P</i> <0.001) were higher among PH patients with AF, compared to compared to those without AF. In propensity score-matched analysis, the odds of in-hospital mortality were significantly higher for patients with AF (OR, 1.298; 95% CI: 1.197-1.379). Similarly, the odds of having greater length of stay (OR, 1.706; 95% CI: 1.658-1.756), and cost (OR, 1.158; 95% CI: 1.079-1.226) were significantly higher for PH patients with AF. <h3>Conclusion</h3> Elderly patients hospitalized for PH with AF have increased in-hospital mortality, hospital length of stay, and hospitalization cost than those without AF. These findings suggest that the presence of AF in PH reflects a more advanced stage of disease. AF may need to be considered as another factor in PH risk scores.