Abstract Mixed micellar systems of cationic gemini 14-s-14 (s=2, 4, 6) and cationic conventional surfactant cetyltrimethylammonium bromide (CTABr) were investigated. The critical micelle concentrations of mixed micelles measured by surface tension, ion selective probe, and conductivity techniques reveal a synergism in the case of 14-2-14/CTABr mixture. Microenvironment and interface properties were studied using bromide selective electrode and by solubilization of a hydrophobic dye Orange OT, solvatochromic dyes Reichardt's betaine and Methyl Orange. Surface potential values, ψ, for mixed micelles are calculated using p-nitrophenol, and are found to be remarkably low for 14-2-14/CTABr systems. These results provide new information for understanding the effect of gemini surfactant structure on the properties of mixed micelles of dicationic/monocationic surfactants.