To provide a decoration cover of simple structure and excellent design for an upper rail for a sliding door which can be installed on the upper rail for the sliding door installed on a wall surface or the like, and an installation structure for that.

This decoration cover A for an upper rail for a sliding door is provided for covering an upper rail R for a sliding door having a U-shaped cross section, opened at a lower part, and fixed on a wall surface, and it is composed of a fixing part 1 to fix the cover to the rail R, and a cover part 2. As an example of the installation structure for the decoration cover A, a lock part is protruded along the whole length of a side surface of the decoration cover on the side of the upper rail for the sliding door, and the lock part is elastically locked to an engagement part provided at a top plate part of the upper rail R for the sliding door.