Bacillus species exhibit potent biocontrol activity against a wide range of fungal pathogens, especially being tested as the most effective prevention strategy for Fusarium oxysporum . This study investigated the antifungal metabolites of Bacillus velezensis NKG-2, a bacterium isolated from the Qilian Mountains in China’s Qinghai Province. Experimental results showed this bacterium exhibited antagonistic activity against major plant fungal pathogens, namely Fusarium oxysporum, Fusarium graminearum, Botrytis cinerea , Alternaria alternata, Fulvia fulva , and Ustilaginoidea virens . In addition, the volatile organic compounds (VOCs) produced by Bacillus velezensis NKG-2 adversely affected the growth of these fungi. We also found that B. velezensis NKG-2 produced chitinase, cellulase, β-glucanase, and amylase enzymes and it promoted tomato plant growth as well, by producing indole-3-acetic acid (IAA) and siderophore. From in vivo biocontrol assay, tomato ( Solanum lycopersicum L.) plants treated only with plant pathogenic fungi showed a disease severity of 65%, whereas bacterial-treated plants lacked any symptoms and their disease severity was only about 25% at the final sampling time. This comprehensive study explored and analyzed many benefits of B. velezensis NKG-2 for its use as a potential biocontrol agent and plant growth promoter, which could be used for improving economic and agricultural development.