The derivatives of cinnamic acid and N-arylpiperazine show antibacterial activity. In this work the potential synergistic effect of cinnamyl derivatives of arylpiperazine in selected bacteria was investigated. The antibacterial activities of the derivatives were evaluated against Gram-positive bacteria: Staphylococcus aureus, Streptosporangium longisporum, Sarcina lutea, Micrococcus flavus, Clostridium sporogenes and Bacillus subtilis and Gram-negative bacteria: Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis and Proteus vulgaris by the disc diffusion method. The minimum inhibitory concentration (MIC) against the selected bacteria was determined for all compounds that showed activity in the disc diffusion method. The majority of the investigated compounds displayed in vitro antibacterial activity. The effect of the type and structure of the substituent on the aromatic ring on the antibacterial activity is discussed. It was found that two derivatives expressed activity toward S. longisporum and P. aeruginosa that was almost as strong as that of amikacin.