A series of N-alkyl pyridinium aldoxime surfactants was synthesized by the reaction of pyridinium aldoxime with long chain alkyl halides (decyl, dodecyl, tetradecyl and hexadecyl bromide). The chemical structure of the synthesized compounds was confirmed by elemental analysis and FTIR spectra. Surface tension was measured in aqueous solutions for different concentrations at 25 °C. Various surface properties of the synthesized surfactants were evaluated, particularly the critical micelle concentration (CMC), effectiveness (π CMC ), efficiency (P C20 ) as well as the maximum surface excess (Γ max ) and minimum surface area (A min ). Also, the micellization and adsorption at liquid/air interfaces were investigated. The synthesized cationic surfactants were evaluated for their biocidal activity. Good antibacterial and antifungal activities were recorded against Gram-positive bacteria ( Bacillus subtilis ATCC 6633, Micrococcus luteus ATCC 25922), followed by Gram-negative bacteria ( Escherichia coli ATCC 23282, Pseudomonas aeruginosa ATCC 10145), yeast ( Candida albicans IMRU 3669) and filamentous fungus ( Aspergillus niger ATCC 16404).