A new colorimetric film using natural dye for detection of ammonia gas was developed and investigated. The natural dye was extracted from Syzygium oleana fruit (ESO). For developing the colorimetric films, the extracted dye was immobilized in chitosan/nanocellulose (CH/NC) films. Color of the natural dye extract was observed to change from reddish purple to purple by the influence of pH ranges from 7-11. Scanning Electron Microscopy (SEM) was used to characterize the CH/NC/ESO films. The results showed that ESO can be combined with CH/NC. Color response of the films toward ammonia gas was evaluated. It was found that the color of the films changes from brownish violet to light yellowish brown after contact with ammonia gas. This result indicates that the CH/NC/ESO films can detect ammonia gas by the way of its color change. The advantages of this colorimetric films are simple, cheap, environmentally friendly, and can be candidate for a label detection of meat spoilage.