In this study, octadecylamine was added into red clay to change its state from hydrophilic into repellent. Direct shear tests on hydrophilic and repellent soils with and without wetting were carried out under different dry densities. Moreover, the variation in the shear strength of red clay without wetting during the transition from hydrophilic soil to repellent soil were investigated, and the influences of wetting on the shear strengths of hydrophilic and repellent soils were tested. Results demonstrated that shear strength of repellent soil without wetting was lower compared with that of hydrophilic soil and that such reduction amplitude increased with the increase in normal stress. Wetting considerably influenced the shear strength of hydrophilic soil but only slightly affected that of repellent soil. The shear strengths of both hydrophilic and repellent soils increased with the increase in dry density. The influences of wetting on hydrophilic and repellent soils were related to dry density and normal stress. Thus, comprehensive considerations should be given to the dry density and stress state of soils when improving the shear strength of wetting soils based on the characteristics of repellent soils.