Laboratory and greenhouse experiments were conducted to investigate the efficacy of a biological control agent (Trichoderma harzianum) against the soil-borne plant pathogen (Fusarium oxysporum f. sp. lycopersici) as compared with a traditional fungicide (Vitavax ® -200). Results indicated that T. harzianum was more effective than Vitavax ® -200 for radial growth inhibition. Through seedling dip and soil application, Vitavax ® -200 was more effective than T. harzianum where it recorded the least wilt incidence comparing to untreated control, but it gave a shorter height of tomato plant than T. Harzianum with significant differences between them. Also, application of T. harzianum as antagonistic agent significantly increased the plant height and increased fruit yield/plant without significant differences with Vitavax ® when compared with untreated control.