A cage assembly comprises a cage, at least one heat sink, at least one clip and at least one light guide. The cage comprises a front end, a rear end, a top wall positioned between the front end and the rear end and a rear wall positioned at the rear end, the cage is formed with at least one port, the port extends from the front end to the rear end. The heat sink is provided on the top wall of the cage and corresponds to one port. The clip comprises a frame engaged with the top wall and fixing the heat sink and a holding piece extending upwardly from the frame. The light guide has a front section and a rear section, the front section is formed with a first post extending rearwardly, the rear section is formed with two second posts respectively extending forwardly, the first post is inserted into a first hole formed to the holding piece of the clip along a front-to-rear direction, the two second posts are respectively inserted into two second holes formed to the rear wall of the cage along a rear-to-front direction.