A 28–year–old female was admitted in view of sudden onset of painful swelling of right lower limb from 3 days. It was found out to be due to an underlying extensive deep vein thrombosis (DVT) of right lower limb. There was no history suggestive for provocation of thrombosis. So, we further evaluated for the cause of this unprovoked DVT. Upon evaluation we ruled out the inherited thrombophilias like Protein c and s deficiency, Factor V Leiden, Dysfibrinogenemia, etc. Lupus anticoagulant was negative. Interestingly, we screened for Antinuclear Antibody and it came out to be Positive. Later Extractable Nuclear Antigen (ENA) profile revealed significant positivity of Anti Smith Antibodies. So, we diagnosed this case as a rare case of Systemic Lupus Erythematosus (SLE) presenting as Unprovoked DVT.