Sodium-affected soils occur predominantly in arid and semi-arid regions. Sodification and solodization are the two main pedogenetic processes in the formation and evolution of these types of soils, in the landscape. In this study, we used soil morphological, physical, and hydraulic analyses to test the hypothesis that sodification and solodization are natural processes of soil degradation, constituting a form of regressive pedogenesis. Sodium-affected Solonetz, Vertisol, and Planosol profiles were sampled and subjected to morphological, physical, and hydraulic analyses. Under the influence of sodification, Solonetz and Planosol showed signs of regressive pedogenesis, including the formation of a surface horizon with sandy texture, weak structure, reduced available water capacity, and evident characteristics of natural erosion. The morphological, physical, and hydraulic properties of Vertisol were not influenced by sodification. Solodization (sodium leaching and topsoil acidification) had a positive effect on the structural characteristics of Planosol, increasing the degree of flocculation (55–100%); thus, solodization was not associated with natural degradation. Sodification and solodization are antagonistic processes. Whereas sodification can be regarded as a form of regressive pedogenesis leading to natural degradation of sodium-affected soils, solodization is a progressive process of profile evolution. Degradation is a natural phenomenon caused by regressive evolution factors during the formation of Solonetz and Planosol profiles. Our results may guide the development of land management strategies for sodium-affected soils in semi-arid regions according to their use capability.