Molecular approaches, internal transcribed spacer(ITS) sequences of ribosomal DNA, and Universal Rice Primer Polymerase Chain Reaction(URP-PCR) were used to investigate the genetic diversity, taxonomic complexity, and relationships of Trichoderma species in mushroom farms. Forty-one isolates of 13 Trichoderma spp. were used in this study and clustered into eight groups. The DNA fingerprint patterns and ITS1 region sequence alignment data showed similar results, but not in some species, such as T. virens, T. atroviride, T. harzianum, and T. aureoviride. Results of this study have proven that the morphology-based taxonomic system has some limitations in terms of classification. The data obtained in this study would be a good index for classifying indistinguishable Trichoderma strains.