Abstract: The use of biological methods in biofertilisation and bio-pest control is essential for the development of agriculture which respects the environment. Various agents have been tested, including micro-organisms. Trichoderma spp., regarding their antagonistic properties against a broad spectrum of plant pathogens, are used the most. Thus, the effect of two Algerian isolates of Trichoderma spp. on growth parameters and crop yield of three varieties of tomato (Lycopersicon esculentum Mill.) has been studied. The results have shown that these two strains have stimulated the growth of tomato plants, including vegetative biomass, but with a predominance of strain TR4. Also, the study found the power of Trichoderma spp. to colonize roots and to remain in the culture substrate. In addition, this study showed the effect of elicitor Trichoderma spp. against Tuta absoluta (Povolny, 1994) ex (Meyrick, 1917). Indeed, the two strains have reduced lepidopteran infestation. The infestation was almost zero for treated plants compared to controls, and this for the three studied varieties.