The Soil Water Characteristic Curve (SWCC) represents the comprehensive physical, mineralogical and water retention properties of a soil. The pore size distribution and air entry head of the soil govern the expansive soil behavior and can be represented indirectly by their SWCC modeling parameters. Hence, the present research targets to study the variation of the SWCC modeling parameters with swell behavior and mineralogy of expansive clays. For this research study, four natural expansive clays having different degrees of expansiveness were selected. The clays were studied for basic soil classification and their clay mineralogy was determined using standard chemical analysis methods. The expansive behavior of the test soils was determined using standard 1-D vertical swell strain tests. The SWCC for all the four expansive soils were determined in the laboratory with the help of pressure cell and filter paper methods. The experimental data were fitted by the van Genuchten (1980) and Fredlund and Xing (1994) SWCC models and the variation of these SWCC parameters with swelling behavior of the soil are studied in detail. From this research, analytical equations involving SWCC modeling parameters and swell behavior were formulated.