Root rot diseasecaused byRhizoctonia solani; is one of the most common destructive tomato diseases. Many different agents i.e., biological agents, chemical inducers and fungicides were investigated for their antagonistic effects on growth of R. solani in vitro. The obtained results showed that, maximum inhibitory effect “100%" was obtained by most tested fungicides i.e. Rizolex–T, Maxim-XL and Moncut followed by salicylic acid at 8mM as chemical inducers. Also, Glomus sp and T. viride as bio-agents were most effective treatments against R. solani where they inhibited the growth of R. solani by 67.22 and 64.07%, respectively followed by oxalic acid at 8 mM and K₂HPO₄ at 15 mM treatments which recorded 59.6 and 44.1%, respectively. Meanwhile, chitosan treatment was the least inhibitive treatment in vitro. Under greenhouse conditions, chitosan was the highest effective treatment in reducing incidence severity of tomato root rot disease as well as increased the assessed vegetative parameters. Moreover, all tested treatments clearly increased the total phenol content and activities of plant defense-related enzymes. As for tomato root anatomy, most treatments increased root diameter of treated tomato plants. Where, T. viride followed by B. subtilis treatments were the best comparing with control treatment.