The adjustable fixator for scanning dental casts includes upper and lower plates which are adapted for releasably securing a dental cast to be optically scanned therebetween. The upper and lower plates are selectively vertically adjustable with respect to one another, and a bottom surface of the lower plate is adapted for releasable mounting in an optical scanner. The upper plate is secured to a cylindrical shell which slidably receives a vertical support mounted to the lower plate, allowing the user to slidably adjust the height of the upper plate with respect to the lower plate. An engaging member mounted to the cylindrical support slides within a vertically extending slot formed through the cylindrical shell. The vertical position of the upper plate may be locked by sliding the engaging member into a selected one of a plurality of horizontally extending slots also formed through the cylindrical shell.