A thin film deposition apparatus and a method of manufacturing an organic light-emitting display device using the thin film deposition apparatus. The thin film deposition apparatus includes a plurality of thin film deposition assemblies, each of which includes: a deposition source that discharges a deposition material; a deposition source nozzle unit that is disposed at a side of the deposition source and includes a plurality of deposition source nozzles; a patterning slit sheet that is disposed opposite to the deposition source nozzle unit and includes a plurality of patterning slits arranged in a first direction; and a barrier plate assembly that is disposed between the deposition source nozzle unit and the patterning slit sheet, in the first direction. The barrier plate assembly includes a plurality of barrier plates that partition a space between the deposition source nozzle unit and the patterning slit sheet into a plurality of sub-deposition spaces.