Abstract This paper looks at the effect of the surfactant and temperature on the complexation of various concentration of 18-crown-6 with aqueous alkali metal salt CsCl. The viscosities and densities of aqueous CsCl solutions with various concentrations of 18-crown-6 were determined in the presence of cationic surfactant, 1-Decyl trimethylammonium bromide (DTAB) at its critical micelle concentration (CMC). Measures were done at 298.15 K and 308.15 K. Excess molar volumes (VE) and the deviations of viscosity (Δη) were obtained using the experimental data. The findings were explained through the molecular interactions and complexation of Cs+ ion with the cavity of 18-crown-6 in the presence and absence of the surfactant. Water is the high polarity solvent therefore Cs+ ion has more solvation. In presence of surfactant reduce the ability of complexation. Generally, at higher temperature hydration of Cs+ ion with water decreases and enhances the complexation between 18-crown-6 with Cs+ ion.