Background: Pocket hematoma is the most common complication after procedures involving cardiac implantable electronic devices (CIEDs). Furthermore, pocket hematomas increase the risk of device infection. Unless severe, a pocket hematoma is usually managed conservatively because specific treatment is unavailable. Aspiration is not recommended as it can cause infection. This study explored whether lowering the risk of infection by aseptically removing the hematoma at an early stage would be possible through aspiration, investigated the effectiveness of treatment with aspiration for pocket hematoma, and analyzed the characteristics of patients with pocket hematoma.Methods: Via chart review, we retrospectively analyzed 570 patients who underwent CIED implantation or replacement between January 2011 and January 2021. Aspiration was performed only on grade 2 and 3 hematomas.Results: Pocket hematomas were identified in 80 patients (14%). Of these 80 patients, 52 (65%) were treated with aspiration only; six (7.5%), with aspiration plus surgical procedure; five (6.25%), with the surgical procedure only; and 17 (21.25%), with conservative treatment. Out of 58 patients treated with aspiration only and aspiration plus surgical procedure, 52 (89.65%) were treated with aspiration only, while six (10.34%) required more procedures (e.g., hematoma evacuation, Barovac insertion, or device reposition with flap surgery). However, none of these six patients exhibited an infection symptom possibly caused by aspiration.Conclusion: Out of 80 patients with hematoma, 58 were treated with aspiration, and none showed infection symptoms that could be caused by aspiration. This suggests that aspiration can be an effective treatment if performed aseptically.