A portable cable vise can be mounted on the edge of a horizontally or vertically extending tailgate, the upper edge of the sidewall of cherry-picker personal bucket, and other support structures in the field. The vise has a lower stationary jaw member and an upper movable jaw member and a means for moving the upper jaw member vertically toward and away from the stationary jaw member to grip a cable between the jaw members. The lower jaw member has an upwardly opening cable receiving recess therein and the upper jaw member has a downwardly opening cable receiving recess therein for gripping the outer surface of a cable without crushing or damaging the cable. The vise includes a generally C-shaped mounting clamp with a clamping means for gripping a support adjacent its edge to secure the mounting clamp to the support. The vise can be secured to the mounting clamp to maintain the vise in a generally vertical orientation regardless of whether the mounting clamp is secured to the edge of a horizontally or vertically extending support.