The experiment was conducted to determine the optimal concentration Naphthalene Acetic Acid (NAA) on the growth and yield of two rice varieties MTL560 and IR50404. The experiments were carried out in two factors completely randomized design with four replications per treatment. The first factor included two rice varieties (MTL560 and IR50404) and the second factor included four levels of NAA (0, 50, 100, 200 ppm). The results show that NAA was not effective on plant height, number of tillers.pot-1, number of panicles.pot-1, filled grain ratio (%), 1000-grain weight. However, NAA was able to improve the number full grains.panicle-1 and grain yield. The highest grain yield (23.7 g.pot-1) was observed in 100 ppm NAA. The yield of MTL560 rice (23.4 g.pot-1) was significantly higher than IR50404 rice (23 g.pot-1).