Abstract: An automatic decapper removes caps from capped test tubes by gripping the cap on a test tube with the upper grippers and holding the cap stationary while the test tube is rotated and translated downward with lower grippers. In a preferred embodiment, the upper grippers comprise three jaws coupled to a cam to be moved, as appropriate, from a first position in which a test tube cap may be inserted between the jaws to a second position in which the jaws grip the inserted cap. The upper grippers are mounted to a decapping arm that is pivotable between a first position above the lower grippers, in which the decapping takes place, to a second position above the exterior of the decapper, where it remains while the test tube is inserted into or removed from the lower grippers and where a removed cap may be released into a container for disposal or reuse. The lower grippers comprise a pair of lever arms for holding the test tube.