A control device for a power transmission mechanism includes a controller. The power transmission mechanism includes an engagement mechanism and an operation mechanism including a movable member and a guide member. The guide member includes a plurality of guide areas being configured to move relative to the movable member to guide the movable member to an engaging position or to a disengaging position. The controller is configured to switch, when determining that a predetermined condition related to traveling of the vehicle is satisfied, a contact guide area that is in contact with the movable member to guide the movable member to the engaging position or to the disengaging position, from a first guide area to a second guide area that are included in the plurality of guide areas.