Objective: To determine the left ventricular systolic dysfunction and the association of various factors with this dysfunction in patients with obstructive sleep apnea syndrome. Study Design: Cross-sectional study. Place and Duration of Study: Pak Emirates Military Hospital, Rawalpindi Pakistan, from Dec 2020 to May 2021. Methodology: We included the patients diagnosed with sleep apnea syndrome by a consultant pulmonologist based on a sleep study. Patients were labelled as having left ventricular systolic dysfunction if the ejection fraction was less than 40% on echocardiography. Results: Eighty patients diagnosed with sleep apnea syndrome were included in the study. The mean age of the study participants was 48.551±9.971 years. Out of 80 patients, 19(23.75%) had left ventricular systolic dysfunction on echocardiography, while 61(76.25%) had no evidence of left ventricular systolic dysfunction. With the application of relevant statistical tests, we found that patients with high body mass index and the presence of comorbid illnesses had a statistically significant relationship (p-value<0.05) with the presence of left ventricular systolic dysfunction among patients with sleep apnea syndrome. Conclusion: Considerable number of patients suffering from obstructive sleep apnea syndrome showed the presence of left ventricular systolic dysfunction on echocardiography. High Body mass index and comorbid illnesses emerged as risk factors for left ventricular systolic dysfunction in our study population.