Trichoderma harzianum is a potential biocontrol agent against Sclerotinia sclerotiorum in soybean. Information is needed on the compatibility of this biocontrol agent and the post-emergent herbicides used in soybean cropping.Haloxyfop R Methyl (EC 10.4%), Glyphosate (SL 48%), Imazamox (WG 70%) and Imazethapyr (SL 10%) were evaluated for their effects on the mycelial growth of T. harzianum on in vitro agar plates. Glyphosate (2000 ppm), Imazethapyr (500 and 250 ppm) and Haloxyfop R Methyl (1000, 500 and 100 ppm) reduced the mycelial growth of T. harzianum . Imazamox had no effect at any concentration.Subsequently, all the herbicides were assessed for their effect on soil populations of T. harzianum . Greenhouse assays conducted with non-sterile soil inoculated with T. harzianum and a specific herbicide were sampled before pesticide application and after 30 days. The number of colony forming units per gram of soil (c.f.u./g of soil) was evaluated with a soil dilution technique using Trichoderma selective medium (TSM). No detrimental effect was revealed.