An adjustable handle assembly is configured for a device that supports and carries a child and that can be moved along a surface. The handle assembly is coupled to a handle extension that extends from a part of the device and that has an end with an extension axis. The handle assembly has a stem configured to attach to the end of the handle extension. The handle assembly also has a grip body coupled to the stem. The grip body is independently movable relative to the handle extension both longitudinally along the extension axis and rotationally about the extension axis. An actuator is provided on the handle assembly and can be actuated between a lock position and a release position. In the lock position, the grip body is in a fixed position relative to the handle extension. In the release position, the grip body is permitted to move both longitudinally and rotationally relative to the extension axis between a plurality of selectable longitudinal and rotational positions. In one example, the device is a stroller that utilizes two such handle assemblies.