Background: The annual incidence of pulmonary thromboembolism is reported to be 39–115 cases per 100,000 population, with rates of 60–120/100,000 in Western countries and 10–20/100,000 in Asian countries. In Mongolia, few studies revealed the prevalence of risk factors and clinical manifestations of acute pulmonary embolism. Over the past 30 years, the incidence of risk factors for non-communicable diseases, which are mainly triggered by lifestyle and social parameters, has rose. Moreover, environmental conditions such as cold climate, hypoxia, and blood hyperviscosit may contribute to higher incidences of acute pulmonary embolism in high-altitude regions. This condition is potentially fatal and can become impair quality of life. Aim: We aimed to compare risk factors and clinical characteristics based on age and sex, and to evaluate laboratory findings and diagnostic tests among Mongolian patients diagnosed with acute pulmonary embolism. Materials and Methods: This retrospective research included total 232 patients meeting inclusion criteria. The information was collected from patient histories, including general demographics, risk factors, comorbidities, symptoms, and physical examination findings. Laboratory analyses included complete blood count, coagulation profile, and immunological markers (D-dimer, NT-proBNP, troponin, protein C, homocysteine, and C-reactive protein), as well as selected imaging parameters. We used Wells and Geneva scoring systems to assess probability of acute pulmonary embolism and Pulmonary Embolism Severity Index to determine disease severity. Differences by age and sex were analyzed using independent t-tests for continuous variables and chi-square tests for categorical variables. Results: Among participants with acute pulmonary embolism, the prevalence of tobacco and alcohol use was significantly higher among males (p<0.001). Among comorbidities, arterial hypertension and other pulmonary diseases were more common in males, whereas cardiac diseases were more frequent in females (p=0.028). Participants aged 65 years and older showed higher rates of comorbid conditions and regular medication use (p<0.001). The most common symptoms were dyspnea (90.9%), chest pain (74.2%), cough (70.5%), leg pain (38.9%), hemoptysis (20.7%), and cyanosis (9.3%). According to sPESI scoring, 69.8% (n=162) were at high risk of death within 30 days, with no significant difference by sex. However, mortality risk within 30 days was significantly higher in participants aged 65 years and above (p<0.001). As increasing age, the neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio were elevated, indicating an acute inflammatory response (p=0.001). Contrast-enhanced CT scans revealed that 95 participants (44.2%) had main pulmonary artery involvement, with no significant sex difference, though involvement of the main pulmonary artery was more frequent in those aged 65 and older. Conclusion Dyspnea, chest pain, and cough were the most common symptoms among patients diagnosed with acute pulmonary embolism. The 30-day mortality risk associated with it was higher among males and increased with advancing age.