I have some experience using SketchUp & Unreal, not Unity. It could be some sort of collision setting (use the actual mesh of the stairs for collision instead of its boundingbox - this is what I have to manually do in Unreal for stairs) OR increasing some step setting allowing the user to 'climb'. Simple google search results in: http://forum.unity3d.com/threads/how-to-get-a-rigidbody-player-to-walk-on-any-type-of-stairs.133573/ https://docs.unity3d.com/Manual/class-CharacterController.html