A hair extension tool simultaneously attaches multiple hair extensions to a recipient's hair. The tool has upper and lower handles that are mechanically coupled in a parallel orientation. The handles are moveable, and the coupling has a quiescent state in which the handles are spaced apart. The tool includes an upper arc and a lower arc that have substantially the same shape. The upper and lower arcs are attached to the handles on their convex sides. The upper arc includes multiple teeth, and each tooth has a substantially semicircular concave opening. The lower arc includes teeth that fit into the openings in the teeth of the upper arc when the upper and lower handles are brought together. Each tooth in the lower arc includes a groove for holding a group of strands of the recipient's hair. The upper arc includes a heating element that is activated by a button.