A self-adjusting trim assembly used at the junction of a wall and ceiling where the wall finishes are to remain stationary while the ceiling is expected to flex due to loads on ceiling structure and normal variations in the height of the supporting structures due to temperature, moisture, creep or other factors effecting the height of the support structures. This trim assembly has two interlocking components comprised of a retainer clip having a vertical back portion (1a), a horizontal projecting tongue (1b) and the interlocking hook portion (1c) and also of a trim strip having a horizontal top portion (2a), a vertical face portion (2b) and an interlocking hook portion (2c) with the vertical face portion of the trim strip designed to cover the gap between stationary wall finishes and a flexing ceiling while trim strip remains flush with the ceiling structure, thus leaving no unsightly gap.