Tensioner devices for use with movable partition systems include endplates configured to be mounted on opposing sides or ends of a movable partition. At least one of the endplates includes a bracket configured for attachment to an end of a chain or a belt. The bracket is movable relative to the endplate. The endplate having the bracket also includes an adjustment mechanism located on a common side of the endplate with the bracket, and is operably coupled with the bracket. The adjustment mechanism is configured for adjusting a distance separating the bracket from the endplate. Movable partition systems include such tensioner devices. Methods of adjusting a tension in a chain or a belt of a movable partition system involve the use of such a tensioner device. Methods of installing movable partition systems within structures include the installation of such tensioner devices.