Abstract: Competition between parasitoid species may be a key factor in shaping size, structure and stability of insect communities as well as an important factor in influencing pest population density and the efficiency of biological control programs. Interspecific competitive interactions between parasitoids exist either between adult parasitoids searching and locating hosts (extrinsic competition) or between larval parasitoids sharing the same host (intrinsic competition). Further understanding the inter- and intraspecific competition in parasitoids and the factors affecting the competition outcome as well as its effect on host suppression could provide implications for selection and management of effective natural enemies in biological control program. We reviewed the interspecific competitive abilities of adult parasitoids in terms of host searching/location strategies and host discrimination, and the inter- and intraspecific competitive abilities of larval parasitoids developing within the same host in terms of physical attack and physiological suppression. This review indicates the necessity to investigate the inter- and intraspecific interactions between parasitoids in agroecosystems.