Postthrombotic syndrome (PTS) is a common complication of deep vein thrombosis. This study aims to assess the role of recurrent venous thrombosis and inherited thrombophilia in the pathogenesis of PTS. A series of 206 patients diagnosed with lower extremity venous thrombosis were retrospectively reviewed. The PTS was observed in 30.58% of the patients. Recurrent venous thrombosis was identified in 3.4% of the patients without PTS and in 33.3% of patients with PTS (P < .001). Inherited thrombophilia alone or in association with recurrent venous thrombosis was more commonly detected when PTS was moderate to severe (P = .04 and <.001) or severe (P < .001). Recurrent venous thrombosis increases the incidence of PTS significantly. The severity of PTS raises when an underlying thrombophilia is present either alone or in association with recurrent venous thrombosis.