Different biological control agents are used to fight various pathogens or even harmful organisms in different environments. Among these agents, a wide range of bacteria belonging to the genus Pseudomonas spp are capable to produce a large number of secondary metabolites with antibacterial activity. The main aim of the present work is the evaluation of the antagonistic activity of Ps. aeruginosa ATCC 27853 against pathogenic bacteria strains such as E. coli ATCC 25921, P. mirabilis ATCC 12453, B. subtilis ATCC 6633 and B. cereus ATCC 11778 by the using agar well diffusion method and by the study of the bacterial growth in the absence and in the presence of the supernatant of Ps. aeruginosa ATCC 27853. In order to characterize the molecules responsible for the antagonistic activity of Ps. aeruginosa ATCC 27853, various parameters such as temperature, pH, and incubation time has been investigated. The obtained results showed that the tested antagonistic activity of Ps. aeruginosa ATCC 27853 against, S. aureus, Enterobacter, S. typhi, P. vulgaris and B. subtilus ATCC6633 has manifested an excellent antibacterial activity with a maximal diameters of inhibition zone 32, 15, 14.14, 13 mm respectively. Furthermore, the study of bacterial growth of B. subtilus ATCC 6633 in the absence and in the presence of the supernatant of Ps. aeruginosa ATCC 27853 indicated a considerable biomass reduction accompanied with unbalanced growth after adding of the supernatant.