A novel rhizobacteria Bacillus was isolated from rhizosphere of soil associated with tomato (Solanum lycopersicum L.) under open field conditions. The Bacillus amyloliquefaciens strain MHR24 (MHR24) is a promising biocontrol agent against several fungal phytopathogens. In this research, MHR24 was characterized by an effective antagonistic ability against Alternaria alternata (Aa), Botrytis cinerea (Bc), Fusarium oxysporum F1 (F1), F. oxysporum F2 (F2), F. oxysporum R3 (F3), and Sclerotinia sclerotiorum (Sc). In particular, MHR24 showed a strong inhibition via airborne volatiles against Bc, F3, Aa, and F2 fungal strains. MHR24 also showed elevated saline stress tolerance at 1% and 25% to NaCl and KCl. The molecular sequence analysis of 16S rDNA confirmed the identity of the isolate as Bacillus amyloliquefaciens strain MHR24. Bioassays on Arabidopsis thaliana Col-0 inoculated with MHR24 showed in in vitro conditions that MHR24 significantly increases the foliar and root area, while in growth chamber conditions, it strongly increases the dry shoot biomass of A. thaliana. The observed results indicate that B. amyloliquefaciens MHR24 has a broad-spectrum biocontrol against fungal phytopathogens and can be used as a biofertilizer and biocontrol agent to improve horticultural crops.