The atomic pair distribution function (PDF) method was used to study the structure of cesium aluminosilicate geopolymer (Cs2O·Al2O3·4SiO2·xH2O, with x ∼ 11). The geopolymer was prepared by reacting metakaolin with cesium silicate solution followed by curing at 50 °C for 24 h in a sealed container. Heating of Cs-geopolymer above 1000 °C resulted in formation of crystalline pollucite (CsAlSi2O6). PDF refinement of the pollucite phase formed displayed an excellent fit over the 10−30 A range when compared with a cubic pollucite model. A poorer fit was attained from 1−10 A due to an additional amorphous phase present in the heated geopolymer. On the basis of PDF analysis, unheated Cs-geopolymer displayed structural ordering similar to pollucite up to a length scale of ∼9 A, despite some differences. Our results suggest that hydrated Cs+ ions were an integral part of the Cs-geopolymer structure and that most of the water present was not associated with Al-OH or Si-OH bonds.