Abstract: A door-mountable cat climbing structure that has a pair of mounting arrangements, at least one of which is biased by a biasing element in a manner that permits adjustment to fit the door while also facilitating secure mounting of the climbing structure thereon. In a preferred embodiment, a biasing element cooperates with a frame of the climbing structure to urge a mounting bracket into engagement with the door while permitting relative movement between the bracket and the door enabling adjustment as well as easy removal. The frame is a generally vertically extending spine from which one or more cat climbing platforms outwardly extend. In a preferred embodiment, the climbing structure includes staggered panels and a spine formed of pairs of adjacent panels coupled together via coupling assemblies that also clamp one of the platforms therebetween in a manner that also extends it outwardly.