The search for new microbial agents for pest control is one of the most important goals in the field of biological control. Some fungal species showed insecticidal activities. Therefore, isolation of more local fungal strains that would be more adapted to the local pest hosts and possesses greater insecticidal activities will be of great value. Studies were carried out in Plant Protection Research Institute, Sharkia branch, Sharkia governorate, Egypt during the period of 2014 to 2015 to survey aphids on some legumes. Trichoderma asperelliodes was isolated from soil, seeds and aphid insects, and was identified morphologically by light microscope and genetically using 18-S ribosomal DNA. Effect of different pH values (5.5, 6.5, 7, 7.5 and 8.5) and temperatures (20, 23, 25, 27, 30, 35 and 40 ⁰C) on T. asperelliodes mycelial growth rates and activity were also studied. The toxicity of T. asperelliodes spore suspension on Aphis craccivora under laboratory condition was examined under electron microscopes (SEM and TEM). The results showed that the optimum environmental conditions for mycelial growth rates of T. asperelliodes were at 30⁰C and pH7.5.  Also, T. asperelliodes has a significant effect in controlling legume aphids with LC₅₀ value of 5.4 x 10⁷ spores ml^-1 and LT₅₀ value of 5.1 days.