Bony mallet injury of the hallux is uncommon. In the few reports of this injury, authors have described surgical treatments such as closed reduction with percutaneous pinning and open surgical fixation with Kirschner wires or a suture anchor. However, the appropriate surgical management for this injury remains controversial. In this article, we describe a case of bony mallet injury of the hallux repaired with the modified extension block techniqueusing 3 Kirschner wires. This method is an effective and simple treatment to allow anatomic reduction of the displaced articular fracture fragment without incision, residual hardware, or the complications associated with open surgical treatment.