A display apparatus for controlling optical transmittance thereof, is provided. The display apparatus includes: a display panel including a pixel having a first region for emitting light via at least one surface thereof and a second region disposed adjacent to the first region and for transmitting external light therethrough; a signal generator for generating a signal including image words representing image data corresponding to the light emitted from the first region, wherein one or more transmittance bits of the signal represent transmittance of the second region; and a transmittance control device for controlling transmittance of the second region based on the one or more transmittance bits.