Six new dodecanoic acid hydrazide-hydrazones (compounds 4a–f), unsubstituted or carrying hydroxy, methoxy, nitro and chloro groups on the benzene ring, were synthesized and tested, in vitro, for their antimicrobial activity against two Gram negative bacteria strains (Escherichia coli and Pseudomonas aeruginosa) and two Gram positive bacteria strains (Bacillus subtilis and Staphylococcus aureus) and two fungal strains (Candida albicans and Aspergillus niger). The microbial screening results indicated that compounds having chloro and nitro substituents were the most active ones. These hydrazone derivatives were characterized by CHN analysis, IR, and 1H NMR spectral data. All newly synthesized compounds exhibited promising results.