In this study, an investigation has been performed on a small-scaled laboratory model and its numerical model by the code of PLAXIS to see the effect of stone columns (SCs) placed vertically in a soft soil slope in terms of slope stability, bearing capacity, and settlements. Also, several hypothetical cases have been examined by the code. Effect of s/D ratios (distance between the vertical axes of SCs/diameter of SCs) was also investigated on slope stability, ultimate bearing capacity, and settlement of a footing rested on top of the slope on the laboratory model. Firstly, ultimate bearing capacity and settlement properties of soil were determined for unreinforced soil that is no SCs were considered. Then, some values of soil were determined after the installation of stone columns with various ratios of s/D. The ratios of s/D were 2, 3, 3.5, and 4. The tests carried out on the laboratory model were simulated and numerically analyzed in two dimensions under plain-strain conditions by Mohr-Coulomb model. In the analyses, PLAXIS computer code, which is based on finite elements method, has been employed. Then, a parametric investigation was carried out to see the effect of SCs on the stability of the slope. In the parametric investigation, several hypothetical cases that were one layer of soil and two layers of soil with the presence of water in the reservoir side of the slopes were examined. The analyses in the investigation were performed by the PLAXIS code for various slope angles beta, ratios of c/(gamma H), and ratios of s/D. From the test results of the laboratory model, and the results obtained from the numerical analyses, it was observed that the bearing capacity of the footing constructed on the top of the slope in soft soil was increased; settlements were decreased after the improvement with SCs. From the analyses performed, it was found that the SCs increased the stability of slope 1.18- to 1.62-fold as a relative effect of different parameters.