Studies on the association between asthma and pulmonary thromboembolism are considerably limited. We investigated whether pulmonary embolism is associated with asthma using a nationwide cohort study. We identified 31 356 patients with newly diagnosed asthma in 2002-2008 and 125 157 individuals without asthma randomly selected from the general population, frequency matched by age, sex and index year using the National Health Insurance Research Database. Both cohorts were followed-up until the end of 2010 to measure the incidence of pulmonary embolism. Cox proportional hazards regression analysis was used to measure the hazard ratio of pulmonary embolism for the asthmatic cohort, compared with the nonasthmatic cohort. We followed 186 182 person-years for asthmatic patients and 743 374 person-years for nonasthmatic subjects. The hazard ratio of pulmonary embolism was 3.24 for the asthmatic cohort, compared with the nonasthmatic cohort after adjusting for sex, age, comorbidities and oestrogen supplementation. The risk of developing pulmonary embolism significantly increased with the increased frequency of asthma exacerbation and hospitalisation. This nationwide cohort study suggests that the risk of developing pulmonary embolism is significantly increased in asthmatic patients compared to the general population. Frequent asthma exacerbation and hospitalisation are significantly associated with pulmonary embolism risk.