In this study, samples of seedlings infected with damping-off symptoms were obtained from different Governorates. A total 102 pathogenic fungal isolates were collected from samples. The pathogenic isolates were frequency percentage as Rhizoctonia solani (9.80%), Fusarium sp. (29.41%), Pythium sp. (7.84%), Penicillium sp. (8.82%), Alternaria spp. (20.59%), Trichoderma sp. (2.94%), Aspergillus sp. (9.80%), Chaetomium sp. (0.98%), Sphaerosorium sp. (0.98%) and unknown (8.82%). Under glasshouse circumstances, the pathogenicity of all 102 fungal isolates was assessed on flax cultivar Giza 12 seedlings. The most effective fungal isolates that decreased survival percentage were F81, RS68, PY97 and Pen58. In vitro, the antifungal activity of six Trichoderma isolates were isolated and tested against four pathogenic fungi (Rs68), (F81), (Py97) and (Pen58). The Trichoderma isolate (T14) was the most effective as it decreased (F81) growth by 78.67%, isolate (T23) inhibited growth by 87% on Pythium (Py97). Also, the isolates of Trichoderma efficiency in controlling damping off of flax seedlings caused by all chosen pathogenic isolates (Rs68), (F81), (Py97) and (Pen58) when tested under glasshouse conditions. In the case of R. solani (Rs68) and Pythium (P97), T14 and T23 showed maximum disease control efficacy (0.00% suppression). In vitro, on differentiate media were used to evaluate the growth performance of Trichoderma spp. Only three as the most potential of Trichoderma isolates were identified as Trichoderma harzianum (T12), T. longibrachiatum (T14) and T. viride (T23). Finally, in flax Trichoderma, could be a safe strategy to use as biocontrol agents for control fungal disease.