This study aimed to evaluate the growth inhibitory effect ofSyzygium aromaticum (clove), Nigella sativa(black cumin), Commiphora molmol (myrrh)and Allium sativum (garlic) on Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii. Water, 80% ethanol and n-hexane plant extracts either alone or in combination were tested against 4 gram negative bacteria. Gel diffusion method, minimum inhibitory concentration (MIC) values were used in this investigation. The findings indicated that individual S. aromaticum, C. molmoland A. sativum extracts had growth inhibitory effect against tested bacteria. Ethanolic extract of S. aromaticum exhibited the highest inhibitory effect on all tested microorganisms. Individual water, ethanolic and hexanic extracts of N. sativa did not show any growth inhibitory effect against all tested microorganisms. Synergistic inhibitory effects of ethanolic and hexanic extracts combination of the four plants were able to prevent the growth of the tested bacteria. Combination of water extracts of the 4 plants inhibit the growth of P. aeruginosa and A. baumannii, while E. coli and K. pneumonia were not inhibited. We are of the opinion that individual ethanolic and hexanic extracts of the clove and combinations of ethanolic and hexanic extracts of the four tested plants could potentially be used for treatment of gram negative bacterial infection especially to the tested microorganisms.