A boiling and stabilization tray has a handle end, shank portion and mouthguard cradle end for supportably receiving and stabilizing a mouthguard for custom fitting. The mouthguard cradle end is connected to the shank opposite the handle end and has a platform for supportably receiving the mouthguard base. An upwardly curved crescent portion engages and supports the anterior and posterior portions of the upward inner lingual wall of the mouthguard. Upwardly curved tabs also extend from the cradle end for engagement with and support of the anterior portion of the upward outer labial wall of the mouthguard. The cradle supports and stabilizes the softened mouthguard during heating, assists in positioning and aligning of the heated mouthguard within the user's mouth, and assists the user in custom fitting of the mouthguard with respect to the user's upper and lower jaw teeth.