Soft clays, such as those found in the Kuttanad region, pose significant challenges to the construction of foundations and infrastructure because of their low bearing capacity, high compressibility, poor shear strength, and high water content. This study aims to improve the strength characteristics of Kuttanad clay (KC) by applying nano-magnesium oxide (N-MgO), portland pozzolana cement (PPC), and a combination of both. The unconfined compressive strength (UCS) of KC treated with various dosages of N-MgO (0.50, 1, 1.50, and 2%) was measured at different curing periods (1, 7, 14, 28, 60, and 90 days) and compared with the strength of KC treated with varying amounts of PPC (1, 2, 4, 6, and 8%) for different curing periods (7, 14, and 28 days). Furthermore, the effect of the combination of N-MgO and PPC on the UCS of the KC was studied. The test results indicate that an optimal combination of 1.50% N-MgO and 1% PPC is sufficient to enhance the strength characteristics of KC, resulting in significant improvements of 370, 421, and 446% in strength after 7, 14, and 28 days of curing, respectively. Durability tests, such as cyclic wetting–drying and acid resistance, were conducted on the treated KC to examine their long-term performance and stability. Microstructural analysis was performed using scanning electron microscopy and X-ray diffraction to understand the interparticle interactions and cementation mechanisms that developed after treatment. In addition, a multivariate linear regression model was used to predict the UCS of treated KC.