This study evaluated the effectiveness of three Trichoderma species (T. viride, T. virens, T. harzianum) for controlling Sclerotium rolfsii, the causal agent of collar rot disease in lentils. In dual culture tests, all three Trichoderma species inhibited the growth of S. rolfsii, with T. harzianum showing the highest inhibition at 63.6%. T. viride most reduced sclerotia formation of S. rolfsii at 91.31%. Volatile compounds from T. viride were also most effective at inhibiting mycelial growth and sclerotia production of S. rolfsii. Culture filtrates