The effectiveness of Clonostachys rosea against Verticillium wilt (Verticillium dahliae) and early blight (Alternaria solani) diseases, as the two most important problems in tomato cultivation with significant economic losses, was determined. It was determined that C. rosea was effective on A. solani and V. dahliae and suppressed mycelial growth. Also, the C. rosea on wheat grains inoculated to plants at 20 g, 30 g, and 40 g concentrations before and after pathogens inoculation. Then, fungal discs (2 mm in diameter) from V. dahliae growing colonies were inoculated on the host plant root zone. A. solani was also inoculated (1x106 conidia ml-1) by spraying the foliar parts of the plants. Results showed that V. dahliae caused 76.0% disease severity in control plants, while the disease severity indices were 58.3%, 55.3%, and 25.3% at 20 g, 30 g, and 40 g C. rosea application, respectively. In A. solani x C. rosea treatments, the disease severities were determined as 96.6%, 63.3%, 43.6% and 46.6% in control, 20 g, 30 g, and 40 g application of C. rosea, respectively. The pathogen suppression rates by C. rosea at 30g application dose was 54.8% against A. solani and at 40 g application dose was 66.6% against V. dahliae. The effects of C. rosea on plant growth parameters were also determined. Results showed that C. rosea had a positive effect on the morphological parameters in tomato plants.