A comparative ecological study of some pre- and post Tsunami isolates of Trichoderma harzianum and T. viride from the Andaman and Nicobar Islands, India, was undertaken to assess the effect on some ecological behavoiur of these biocontrol agents. All the isolates showed better parasitic ability and rhizosphere colonization when the competition of other organisms withdrawn compared to natural and sun dried soil. Both competitive parasitic behaviour and rhizosphere colonization was low in post-Tsunami isolates of Trichoderma. The chlamydospore inoculum was found best in percentage colonization of sclerotia of boh R. solani and S. rolfsii, followed by mycelial and conidial inoculum. The isolate ThrAN-5 (T. harzianum) was most efficient in parasitizing the sclerotia of S. rolfsii and R. solani, followed by TvAN-3, TvAN-5 and ThrAN-7 (Pre-Tsunami isolates), whereas there was significant reduction in their parasitizing ability of post-Tsunami isolates. Similar results were also noted in their rhizosphere colonizing ability in rhizosphere of chick pea seedlings. All isolates of Trichoderma showed significantlty low competitive parasitic ability and rhizosphere colonization in Mohanpur (B.C.KV.) soil as compared to Port Blair (CARI) soil.