Thoracentesis is considered a relatively safe and well-established procedure commonly done at the bedside with minimal risk of complication. Thoracentesis-related hemothorax is uncommon; however, it may be life-threatening. We describe a case of a 19-year-old woman with persistent fever and pleural effusion, in which thoracentesis resulted in tension hemothorax due to intercostal artery laceration. It is important for proceduralists to understand not only the tortuosity of the intercostal artery covering 25% to 50% of the intercostal space, but also the presence of traversing collateral arteries. Herein, we discuss the potential benefit of vascular ultrasonography with color Doppler during thoracentesis, with the goal of avoiding vessel injury and hemorrhage.