OBJECTIVES: Warfarin is an oral anticoagulant prescribed as prophylaxis for patients with high risk of developing thrombosis, pulmonary embolism as well as treatment for recurrent and idiopathic incident of pulmonary embolism. This study aims to compare time in therapeutic range (TTR) of warfarin in patients with pulmonary embolism with bleeding and stroke and determine reasons of INR falling out of range.  METHODS: This is a retrospective study carried out at a tertiary-care hospital with anticoagulation clinic in the state of Selangor, Malaysia. The samples of the study were patients with pulmonary embolism, prescribed with warfarin from year 2009 to 2014. The data collected includes patients’ demographics, co-morbidities, and international normalized ratio (INR). TTR was determined using Rosendaal method. Patients' stroke, haemorrhage events and reasons of INR being outside the range were recorded. RESULTS: TTR of 20 out of 30 patients (66.67%) were found to be outside the range (<75%) with 8 of them (40%) experiencing bleeding. The remaining 10 patients (33.33%) recorded TTR of more than 75%, where 3 of them (30%) experienced bleeding during their warfarin treatment. Out of the total 11 patients who bled, 10 of them had minor bleeding. The other 1 patient from TTR <75% group had major bleeding. None of the patients from both groups experienced stroke. The highest identified reason of International Normalized Range (INR) being outside the range was found to be drug-drug interactions, which were seen in 9 patients (30%). CONCLUSIONS: Warfarin treatment should be maintained within the targeted INR range to avoid unwanted events such as bleeding and stroke. Based on the findings of this study, it can be concluded that warfarin monitoring should be done continuously and thoroughly to ensure that INR level falls within the targeted range.