Aphidius matricariae Haliday and Praon volucre (Haliday) (Hymenoptera: Braconidae) have been commercially used to control of Aphis gossypii Glover (Hemiptera: Aphididae) in greenhouses. Today, biological control agents are frequently used in combination against pests in greenhouses. In some cases, interaction between two biological control agents may lead to competition and therefore affect the success of biological control programs. Interspecific interaction between parasitoid wasps may be a key factor in the community dynamics of host-parasitoid systems and in the selection of effective biological control agents. In this study, effect of interspecific interactions between A. matricariae and P. volucre on their population dynamics on A. gossypii on cucumber (Super Sultan variety) in transparent plastic cage (40×40×40 cm) were investigated under greenhouse condition, at 25±2°C, 60±5% relative humidity and a photoperiod of 14: 10 (Light: Dark) h with 4 replications. Population dynamics were examined based on the Box–Jenkins methodology as a time-series modeling procedure. The mean population size of A. matricaria and P. volucre significantly decreased by interspecific interaction. When parasitoids acted alone, CV values of A. matricariae and P. volucre were 1.50 and 0.52, respectively. But when both parasitoids acted together, CV values of A. matricariae and P. volucre were 1.34 and 1.01, respectively. The lower value of CV shows more stability or low variation in population size of parasitoid wasps. Repeated measures analysis revealed a significant effect of interspecific interaction (with remove the time effect) on the population size of both parasitoids. The results of time series experiment of A. matricariae and P. volucre on A. gossypii revealed that interspecific interaction of parasitoid wasps had significant effect on population dynamics of A. matricariae and P. volucre. Their interspecific interaction of these parasitoid wasps was direct density-dependent before interspecific interaction. But after interspecific interaction, population dynamics of A. matricariae and P. volucre change to density-independent process. The results of this research may be useful in the management of A. gossypii by combination of A. matricariae and P. volucre on cucumber in greenhouses.