<p>This article presents first-of-a-kind experimental works for the conversion of tailings generated from an Indian uranium mill into geopolymers. Geopolymer block samples were prepared from uranium mill tailings by alkali activation method using 4–6% NaOH and 27–39% Na₂SiO₃. The key physical, mechanical, and most importantly radiological characteristics were evaluated. The geopolymer blocks exhibited acceptable compressive strength (&gt; 3.5&#xa0;MPa) and low radon exhalation rates (2.62–20.42 Bqm⁻²&#xa0;h⁻¹). Radium equivalent activity (512–761 Bqkg⁻¹) in the geopolymer blocks was in the acceptable range for construction activities. Million tons of mill tailings generated annually from uranium ore processing facilities are potential sources of construction materials.</p>