1-(Dialkylaminomethyl)-2-(p-substituted phenyl)-5-substituted benzimidazole derivatives 1 have been synthesized by reacting 2-phenylbenzimidazole derivatives with formaldehyde: and a secondary amine. The derivatives of 2-phenylbenzimidazole were obtained by reacting the bisulfide addition product of substituted benzaldehydes with 4-substituted-o-phenylenediamines. Their structures were confirmed by microanalysis, IR and NMR spectral analysis. Antimicrobial activity of the compounds was investigated by the microdilution susceptibility test in Mueller-Hinton Broth and Sabouraud Dextrose Broth was used for the determination of antibacterial and antifungal activities Test organisms: Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 as Gram-positive bacteria, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 as Gram-negative bacteria. and Candida albicans, C. parapsilosis, C. stellatoidea as yeast-like fungi. Compounds 1a, 1b; 1c, 1e and 1i showed slight to moderate activity against all microorganisms. Compound 1g showed the highest activity. It was found more potent than streptomycin against Enterococcus faecalis and Pseudomonas aeruginosa.