BACKGROUND Fractures of the clavicle are extremely common, representing 2.6-12% of all fractures and 35-44% of all shoulder girdle injuries; 69-82% of these fractures occur in the middle third of the clavicle. Vascular injuries relating to clavicle fracture are usually due to extreme force applied to the clavicle in an acute setting. No other reports of delayed subclavian vein laceration were found on literature search. OBJECTIVE We present this case to increase awareness among emergency physicians of the potential delayed presentation of this rare condition. METHODS A 21-year-old man presented to the Emergency Department with acute swelling of the base of the neck after carrying a heavy load on his left shoulder the night before. He had been recovering from a clavicle fracture for 2 months. Malunion of his left midshaft clavicle fracture led to subclavian vein injury and formation of a large hematoma secondary to reinjury that occurred at work the night before presentation. Computed tomography revealed a 9-cm hematoma at the fracture site. The patient was found to have a subclavian vein injury without evidence of arterial injury or nervous system involvement. The patient was admitted for observation and subsequently discharged without need for surgical intervention. CONCLUSIONS Subclavian vein laceration is a rare complication of clavicle fracture. Patient education at discharge after conservative management is important due to the risk of vascular complications from malunion and reinjury.