Mixed micellization behavior of three dimeric cationic surfactants alkanediyl-alpha,omega-bis(tetradecyldimethylammonium bromide) (referred to as 14-s-14, where s = 4, 5, 6) with two cationic conventional surfactants (hexadecyltrimethylammonium bromide and tetradecyltrimethylammonium bromide) have been studied using conductance and fluorescence techniques. Critical micelle concentration for different mixing mole fractions, their ideal values, interaction parameters, micellar mole fractions, and activity coefficients have been evaluated using Rubingh's theory. Motomura's theory is also used to calculate the micellar mole fractions. All these parameters indicate nonideal but synergistic behavior. Aggregation numbers from fluorescence quenching suggest that contribution of the conventional surfactants is always greater than that in the ideal state.