Heparin Induced thrombocytopenia (HIT) is a rare, immune-mediated complication of heparin, associated with both thrombocytopenia and paradoxical thrombotic events. Initial diagnosis is made clinically when platelet count falls by 30% to <100 × 109cells/l or a > 50% decrease from baseline count in association with heparin therapy. Thromboembolic complications are seen in 50% of the cases. We present a case of acute pulmonary embolism (aPE) in a 65 year old male secondary to HIT while on unfractionated heparin for venous thromboprophylaxis. He was admitted to the hospital for severe acute exacerbation of asthma and was on heparin and venodyne boots for venous thrombo-prophylaxis. His chief presenting complaints improved until day 13, when he had severe pleuritic chest pain with worsening of shortness of breath and was desaturating while breathing ambient air. Computed tomography (CT) of the chest with intravenous contrast revealed aPE involving bilateral upper lobe segmental pulmonary arteries. Given the pattern and timing of thrombocytopenia prior to onset of his symptoms and acute thromboembolism, diagnosis of HIT was made which was later supported by positive platelet factor- ELISA and serotonin release assay (SRA) laboratory testing. Heparin and heparin-related products were promptly discontinued and argatroban was started. Later platelet count increased over 150 × 103/μL and argatroban was switched to warfarin prior to discharge. As heparin is extensively used, all physicians are required to be attentive of this life threatening complication. Discontinuing heparin while substituting with an alternative anticoagulant such as argatroban may become a life-saving strategy in such a case.