Population growth in the southern United States is rapidly increasing the construction of civil infrastructure on expansive soils. However, these soils cause difficulties due to the moisture-fluctuation-induced swell-shrink behavior of expansive soils. Traditional calcium-based stabilizers, such as lime and cement, that are effective in mitigating the swell-shrink potential and improve the engineering properties of expansive soils, are generally used to stabilize expansive soils. Despite these advantages, stabilization of sulfate-rich soils using the calcium-based stabilizers results in sulfate-induced heave due to the formation of a highly expansive mineral, ettringite, which is mostly observed to be counter-productive. The manufacture of calcium-based stabilizers is also not eco-friendly as it releases large amounts of carbon dioxide. This study investigates the suitability of using a metakaolin-based geopolymer as an environmentally friendly soil stabilizer for treating sulfate-rich soils. A comparative study was conducted by performing one-dimensional free swell tests on geopolymer-treated, lime-treated, and untreated soil specimens to assess the benefits of using a geopolymer in effectively stabilizing the sulfate-rich expansive soil. The results of the swell test show that sulfate-rich soil treated with a geopolymer is more effective at reducing the swelling potential than soil treated with lime. Therefore, geopolymer shows promising potential as an alternative material to traditional soil stabilizers in sulfate-rich areas.