Background/Objectives: Obstructive sleep apnea (OSA) and pulmonary embolism (PE) share several risk factors, while emerging evidence suggests a potential patho-physiological link beyond these common determinants. We aimed to characterize the prevalence and severity of OSA in patients with acute PE and to investigate whether the apnea-hypopnea index (AHI) is independently associated with PE and its clinical course. Methods: In this prospective, single-center, case–control study, 128 consecu-tive patients with acute PE and 252 outpatient controls with other respiratory diseases underwent home respiratory polygraphy. In patients with PE, the sleep study was per-formed at least three months after the acute event. OSA was diagnosed and graded according to international consensus criteria. Logistic regression models were used to evaluate associations between AHI and PE, acute PE severity, chronic deep vein thrombosis (DVT), and venous thromboembolism (VTE) recurrence. Results: OSA was present in 55.5% of patients with PE, with severe OSA in 28.9%, compared with 42.1% and 13.9%, respectively, among controls (p = 0.013 and p = 0.001). Patients with PE had a higher AHI (21.21 ± 19.29 vs. 14.81 ± 14.26 events/h; p = 0.007) and oxygen desatura-tion index (19.86 ± 18.77 vs. 13.30 ± 13.79; p = 0.003). Each 10-events/h increase in AHI was independently associated with PE after adjustment for age, sex, BMI, and estab-lished VTE risk factors (OR 1.205, 95% CI 1.019–1.426; p = 0.029). AHI was not inde-pendently associated with intermediate-high/high-risk PE or chronic DVT. Among pa-tients who discontinued anticoagulation, VTE recurrence was higher in those with OSA (36.0% vs. 13.3%; p = 0.049). Conclusions: OSA is highly prevalent and frequently severe in patients with acute PE. Increasing AHI is independently associated with the presence of PE, supporting a clinically relevant link between sleep-disordered breath-ing and thromboembolic disease. Whether OSA contributes to recurrent VTE after an-ticoagulation withdrawal requires confirmation in larger prospective studies.