Abstract: A locking mechanism for the control cords of a window blind extends partially into the headrail of a window blind, and a cord separation member on the portion of the mechanism within the headrail has discrete openings through which the cords pass and are separated as they enter the mechanism. A guide pin is positioned transversely across the upper end of the mechanism with one end of the guide pin being disposed nearer the separation member and lower than the other end, so that the cords passing over the pin may be rotated to a selected side of this portion of the mechanism. A cord gripping means is mounted below the guide pin, and includes a fixed gripping member disposed centrally within the second portion of the mechanism, and a movable gripping member is mounted within this second portion of the mechanism for gripping the cords therebetween. The separation member, guide pin and movable gripping member are all positionable alternatively for either left hand or right hand operation of the locking mechanism.