Trichoderma is an antagonist fungus used in agriculture and forestry for the diseases control. The use of the herbicides metsulfuton methyl and glyphosate is a common practice for weed control that limits Trichoderma use. This study has evaluated the toxic effects of the herbicides metsulfuron methyl and glyphosate on four strains of fungi of the genus Trichoderma (GRB-HA1, GRB-HA2, GRB-HA8 and GRB-HA9). Poisoned media were prepared with high doses of 25 mL·L-1 of glyphosate + 0.2 g L-1 of metsulfuron methyl (D500) and low doses of 12.5 mL·L-1 of glyphosate + 0.2 g L-1 of methyl metsulfuron (D250) to determine the effects on viability. The effects of the exposure time (30-90 min) on the germination of the conidia were determined using suspensions prepared with the mixtures D500 and D250. The results showed the differential sensitivity of the Trichoderma strains that affected the viability of the conidia and mycelial growth. © The author; licensee Universidad Nacional de Colombia.