In present research, three plant growth-promoting (PGP) non-pathogenic bacterial strains Proteus mirabilis BUFF12, Pseudomonas aeruginosa BUFF14 and Enterobacter xiangfangensis BUFF38 inhabiting buffalo dung identified and studied for antifungal activity. Among three, P. mirabilis showed broad spectrum antifungal activity against Fusarium oxysporum (62.7%) and Rhizoctonia solani (71.7%). FTIR spectral analysis of crude ethyl acetate extract of P. mirabilis showed the presence of O-H, N-H, O=C=O, C=O, C=N, CH2, C-O, C-H, PO2-, and C-C functional groups. GCMS spectral analysis displayed the presence of eleven bioactive metabolites and the major compounds were 2-cyclopenten1-one, 3-(acetyloxy) (23.87%) followed by Glutarimide, N-(4-ethylphenyl)- (19.34%); 4-methyl-2-oxopentanenitrile (14.49%); 2,3-Cyclododecenopyridine (13.40%). The purified compounds also established multifarious PGP activity in test crop plants during pot study for disease management. 2-cyclopenten-1-one,3-(acetyloxy) recorded significant inhibitory activity against F. oxysporum (62.7%), followed by R. solani (71.7%). Pot trial studies with this strain significantly reduced disease severity in fennel plants challenged with F. oxysporum and R. solani infection. Our findings provide new insights into the antifungal activity of P. mirabilis, and suggest this species may a promising candidate as a biocontrol agent to confer resistance to gummosis and foot rot and other phytopathogens in fennel crop.