If there is a weight limit I probably have challenged it. When our son was younger I often had to swap beds with him because he would get scared on the ship. This was often an upper berth. I weigh around 230 and never felt the bunk was in danger of collapsing. However, they are not especially long bunks so your son's biggest issue may be with his height! They have a small ladder they put up at night for access to the upper bunk. When you return from dinner, your cabin will be set up for sleeping with the upper bunk opened up and the ladder attached.