Tomato southern blight disease caused by Scelerotium rolfsii is very common in tropical and subtropical regions in the world. Using chemical fungicides is not very successful in this plant disease management as the pathogen has not only wide host range but also the ability to produce sclerotia which are able to survive for many years in the soil. As an alternative eco-friendly approach to control the disease, a biocontrol agent (BCA) Trichoderma species and a plant defense inducer were used in this study. Four different treatments were applied in the greenhouse environment. Results from this study show neutralized phosphorous acid salts (NPS) treatment and the tomato accession are the main factors to affect the tolerance against the pathogen. Moreover, two trials for testing the effect of BCA show the application time might play an important factor to raise the survival ratio of tomato seedlings. Overall results from the present study may be concluded that choose a tolerant host plant, adding NPS or Trichoderma spp. 3 days before the infection could be some useful strategies for tomato southern blight management.