The cage itself is easy enough to assemble...that is, if all the pieces come in correctly. The bottom door of our's was broken (couldn't pull the trigger hinge for the top lock) so we had to rip the top lock pin out to get it to work as it was permanently jammed. We didn't have time to wait for a replacement part. Some pieces don't fit together well and you'll be struggling to make it fit. The top also has a one inch gap in some places, not sure if that's supposed to happen? You will need 2 people to put this together, and if a cat jumps around in it you're going to hear it. All in all, it's not terrible because our cat loves it, just wish it was of better construction.
Side note: When you get this, most likely all of the styrofoam will be dust. Make sure you have your vacuum close...it was styrofoam piece city in our place for three days and several vacuuming attempts.