Transmission electron microscopy is used to investigate electron‐induced crystallization of thermally evaporated amorphous AlF3(a‐AlF3). It is shown that this material undergoes a very complicated crystallization process with three crystalline substances (Al, AlF3, and Al2O3) formed as the dose increases. The sequence of the crystallization is highly sensitive to the presence of water, which inhibits radiolytic dissociation of a‐AlF3 into Al and fluorine, reduces the dose required for the crystallization of a‐AlF3, and causes the transformation of AlF3 into Al2O3.