Background: The prevalence of acute pulmonary embolism (PE) among patients hospitalized with pneumonia and its association with adverse outcomes remain uncertain. Methods: Data from the US National Inpatient Sample between 2016 to 2020 was used to determine the proportion of patients with chief diagnosis of pneumonia that had concomitant PE and to examine the relationship between PE and in-hospital outcomes such as mortality, mechanical ventilation, thrombolysis, length of stay (LoS), and inpatient costs. Results: A total of 13,956,485 patients with a diagnosis of pneumonia were included and 2.6% had a concomitant diagnosis of PE. The median LoS for patients with PE was 7 days, compared to 5 days for those without PE. The median hospitalization cost was higher for patients with a diagnosis of PE compared to those without PE ($16,917 vs. $10,656). The strongest factors associated with a diagnosis of PE were other venous thromboembolism (Odds Ratio (OR) 11.65, 95%CI 11.42-11.88, p<0.001), arterial thrombosis (OR 2.64, 95%CI 2.40-2.89, p<0.001), previous venous thromboembolism (OR 1.72, 95%CI 1.68-1.77, p<0.001), cardiac arrest (OR 1.69, 95%CI 1.62-1.77, p<0.001) and cancer (OR 1.45, 95%CI 1.42-1.48, p<0.001). Co-diagnosis of PE was associated with greater in-hospital mortality (OR 1.50, 95%CI 1.46-1.54), mechanical ventilation (OR 1.12, 95%CI 1.10-1.15), thrombolysis use (OR 6.69, 95%CI 6.31-7.09), and major bleeding (OR 1.48, 95%CI 1.39-1.57). Conclusions: A diagnosis of PE occurs in 2.6% of patients hospitalized with a principal diagnosis of pneumonia. Having concomitant PE was associated with greater risks of in-hospital mortality, increased use of mechanical ventilation and thrombolysis, extended hospital stay, and higher inpatient costs.