Background Deep vein thrombosis (DVT) is commonly identified and diagnosed in the emergency department. Factors including sedentary life (immobility), pregnancy in women, cancer, postoperation, admission to ICU, smoking, and obesity are identified risks for thrombosis development. We report a case of a 35-year-old man who presented to the emergency department developing left lower leg swelling and pain, low-grade fever, and headache after he was treated and discharged, cured of severe COVID-19. Then venous and arterial Doppler ultrasound of the lower leg revealed dilated, absent flow and luminal thrombus in the distal popliteal, anterior and posterior tibial veins and perforator vessels were diagnosed as leg DVT. Conclusion DVT is a hematological emergency that needs serious consideration in prevention as well early diagnosis in patients with possible risk factors. This case report aims to arouse the clinician’s awareness of the occurrence of deep vein thrombosis during and after COVID-19.