I believe the lens could fit in the case. The side supports can be moved around and the velcro allows you to make changes to the shape and length of the areas. I have a 55 MM (on camera), a 200 MM lens (above camera in the middle), a 300 MM on one side and a speedlight on the other side in my case. Depending on the length of the 500 MM lens you may be able to put it in the side area separate from the camera. I would measure it to be sure. I am not sure the case is long enough so that you could leave the 500 MM on the camera body and have it fit. I can put my 55 MM on the camera body and put my 200 MM lens above it inline, if that helps any.