Wild oat (Avena fatua L.) is a problematic weed of wheat (Triticum aestivum L.) in Pakistan. The present study was designed to evaluate the herbicidal activity of culture filtrates of four Trichoderma spp., namely T. harzianum, T. pseudokoningii, T. reesei and T. viride, against this weed species. In a laboratory bioassay, original (100%) and diluted (50%) culture filtrates of T. harzianum and T. pseudokoningii significantly reduced shoot and root growth of A. fatua seedlings. Only original culture filtrates of T. reesei exhibited significant effects, while the effect of filtrates of T. viride was insignificant against shoot and root growth of the target weed species. Generally, original concentrations of culture filtrates of all Trichoderma spp., except T. harzianum, significantly reduced various parameters of root and shoot growth of wheat seedlings. In foliar spray bioassay, pot-grown 1-wk and 2-wk old A. fatua and wheat seedlings were sprayed with 100% culture filtrates of the four Trichoderma spp. thrice with 5 d interval each. Culture filtrates of all except T. viride significantly diminished root and shoot biomass of A. fatua plants in 1-wk old plants. The effect of foliar spray on root and shoot growth of wheat was insignificant. Present study concludes that metabolites of T. harzianum, T. reesei and T. pseudokoningii contain herbicidal constituents for the management of A. fatua.