Abstract: Experiments were carried out to correlate the biochemical features of Trichoderma species and Rhizobium leguminosarum to both biocontrol of Botrytis fabae and improving the productivity of faba bean. Of several Trichoderma species, isolated from phyllosphere of faba bean, six isolates, which grew considerably faster than B. fabae and have moderate to very good antagonism against this pathogen, were selected. Trichoderma’s growth inhibiting properties of B. fabae were due to the combined action of non-volatile and volatile metabolites (with antibiotic nature) and the secretion of cell-wall degrading enzymes. Trichoderma viride (tag3 and tag4) and T. harzianum tag7 have shown to be efficient mycoparasites on B. fabae (in which the mycelium appeared to be fragmented hyphae, vacuolated and disrupted as a result of Trichoderma parasitism). These three Trichoderma isolates were further applied in field of faba bean combined with R. leguminosarum which, the chromatographical analysis of its supernatant showed activity in growth promoter substances. The dual inoculation of seeds with a mixture of R. leguminosarum and T. viride tag4 then foliar spraying of the developed plants with the spore suspension of the same T. viride tag4 at the 35th and 55th day from sowing reduced chocolate spot disease and enhanced nodulation, nitrogenase activity and nitrogen fixing bacterial population in the rhizosphere. In addition to the improvements in the physiological activities (photosynthetic pigments, total phenol and polyphenol oxidase), plant growth and yield. On average, this treatment recorded about 57% reduction in chocolate spot disease and 23% increase in faba bean yield, compared to control plants. Therefore, a commercial production of an inoculum based on a mixture of Rhizobium and Trichoderma is very encouraged.