Nowadays, Rose is one of the best-selling flowers all over the world. Given that, the western flower thrips called Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) is one of the most important pests of this flower in the greenhouse. In order to control this pest, the most recently common method is the chemical method in which a lot of pesticides are used. Considering the risks of unnecessary consumption of pesticides and harmful effects on the environment, it is necessary to estimate the economic injury level of the pest to reduce the risks of pesticide use as well as the beneficial control and management of this pest. Therefore, in order to determine economic injury level of this pest, an experiment was conducted in a rose greenhouse in Yasouj city with a total area of 112 m2 during a period of six months on the Angelina variety of rose. First, a weekly number of pests was sampled as a direct counting per unit area, then the number of flowering branches which were removed due to the damage caused by the feeding of the thrips were recorded. According to the estimated mean of the pest, the damage caused by each thrips was also calculated. Regarding the cost of the chemical control of this pest in one hand, and the success rate of that method in pest control in the other hand; as well as the price of each rose flower, economic injury level of the pest was estimated to be 19.04 insect per m2 and2.72insects per bud. This insect number includes the adult and immature stages of the western thrips flower. In short estimation of this level can lead to beneficial control in the rose greenhouses.