Fusarium oxysporum f.sp. lycopersici (FOL) is one of the most important fungi causing vascular wilt disease of tomato plants. Many different agents i.e., Bacillus subtilis, Trichoderma harzianum, T. viride, alga (Sparulina platensis), Mycorrhiza (Glomus sp.) and potassium humate were investigated for their antagonistic effects on the growth of FOL in vitro. T. harzianum and potassium humate were the most effective treatments, followed by B. subtilis and alga extract. The previously mentioned treatments were studied under greenhouse conditions and natural infection in the field. T. harzianum and potassium humate were the most effective treatments against FOL followed by B. subtilis and alga extract. Mycrrohiza was the lowest effect treatment under greenhouse and field conditions. T. harzianum and potassium humate decreased the activities of hydrolyzing enzymes and increased all of total phenols and plant parameters (fresh, dry weight and length/ plant) of treated tomato plants.