Abstract: Nematodes of the genus Meloidogyne are obligate parasites that infect a wide range of different crops in all agricultural regions worldwide and cause significant losses of both yield and quality of produce. Trichoderma spp. have long been known to be a feasible biological alternative to chemicals for control of several soil-borne plant pathogens. More recently, it has been shown that Trichoderma spp. may be effective also in control of plant parasitic nematodes. However, very little is known on the mechanism(s) by means of which these antagonistic fungi can limit nematode infestation. In order to assess the capability of the antagonistic strain T. harzianum ITEM 908 to elicit resistance to M. incognita in tomato plants, we investigated the expression of the genes PR-1 (marker of the salicylic acid-depending resistance signalling pathway, SAR) and JERF3 (marker of the jasmonic acid/ethylene-depending resistance signalling pathway, ISR) during the interaction between ITEM 908 and M. incognita on susceptible tomato plants. Our findings suggest that jasmonic acid/ethylene-mediated resistance to M. incognita, is induced in tomato roots by treatment with T. harzianum ITEM 908, whereas, salicylic acid-mediated resistance, seems not to be involved in the interaction between this strain and tomato plants, at least in the roots. We also investigated the effect of T. harzianum ITEM 908 on infestation parameters, such as egg mass production, female fecundity and reproduction potential of M. incognita on the infested tomato roots. The presence of a suitable amount of T. harzianum ITEM 908 in soil (106 CFU/g of rhizosphere soil) significantly reduced all of the infestation parameters investigated. It is still to be established whether nematode infestation is reduced by ISR induction in roots or by a putative nemato-static and/or nemato-toxic activity of ITEM 908 in the soil, or a combination of both.