Currently, research based on the technology and applications of 3D printing is being actively pursued. 3D printing technology, also called additive manufacturing, is widely and increasingly used in the medical field. This study produced custom casts for the treatment of mallet finger using plaster of Paris, which was traditionally used in clinical practice, and 3D printing technology, and evaluated their advantages and disadvantages for patients by conducting a wearability assessment. Mallet finger casts produced using plaster of Paris, when incorrectly made, can result in skin necrosis and other problems for patients. These problems can be mitigated, however, by creating casts using 3D printing technology. Additionally, plaster casts or ready-made alternatives can be inconvenient with respect to rapid treatment of patients. In contrast, 3D-printed casts appear to provide patients with appropriate treatment and increase their satisfaction because they are small in size, custom-made for each patient, and can be quickly made and immediately applied in clinical practice.