Abstract: A foldable toothbrush has a shell, a cover, a mounting sleeve, a handle and multiple bristles. The cover is mounted pivotally to the shell and selectively covers the top opening and part of the front opening of the shell. The mounting sleeve is mounted pivotally to the shell and is selectively pivoted into the shell. The handle is mounted in the mounting sleeve and is selectively rotatable and slidable in the mounting sleeve. The bristles are attached to the handle. With the handle being rotatable and slidable in the mounting sleeve, the whole length of the toothbrush is adjustable to selectively adapt for using or stowing. Furthermore, the cover keeps the handle and the bristles clean when stowing.