A cable tensioner for adjusting the tension in various cables. It may be used with a variety of cables including those that have flexible members routed through bendable sheaths. The cable tensioner includes a worm gear arrangement located within a housing, where the worm gear takes the form of a worm screw engaged with a spur gear. The spur gear may then be engaged with teeth on a movable sleeve. The end of a cable is secured within the sleeve and the tension in the cable can be adjusted by moving the sleeve via the worm gear.