Problem statement: Sclerotinia sclerotiorum and Sclerotium cepivorum are soil pathogens which have generated resistance to synthetic fungicides. One biological alternative to this problem is to select novel strains of Trichoderma with different mechanisms of action against these plant pathogens to ensure efficient control. Approach: In the present research was determined the antagonism effect of Mexicans Trichoderma strains on S. sclerotiorum and S. cepivorum in vitro. It was used dual culture technique by determining the percentage of mycelia growth inhibition, days to contact and antagonism levels proposed by Bell. It was also determined the effect of volatile compounds and metabolites compound from Trichoderma produced in solutions. Results: The mycelia growth inhibition of S. sclerotiorum and S. cepivorum were 45-63.8 and 50.9-81.5% respectively by the effect of Trichoderma strains. The T. ghanense and T. longibrachiatum (T15 and T10) inhibited in higher proportion to S. sclerotiorum. On the other hand T. inhamatum and T. asperellum (T32 and T11) inhibited in higher proportion to S. cepivorum. The days to contact between the Trichoderma and phytopathogen species were between two to three days. The levels of antagonism according to the Bell's scale were different between the two species of phytopathogen and for Trichoderma strains were grouped into I and II class. The maximum inhibition effect by volatiles compound was occasioned by T. longibrachiatum with 31.5 (T3) and 59.2% (T10) on S. sclerotiorum and S. cepivorum respectively. Respect to metabolites, these shown high effects on phytopathogen growth, where T. asperellum is the more outstanding specie which produce totals mycelia growth inhibition of two phytopathogen species. Conclusion: T. longibrachiatum (T3 and T10) and T. asperellum (T1 and T11) were the most efficient species with the highest antagonist effects against S. sclerotiorum and S. cepivorum.